1910 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

BIOLOGY 

Class       L1B*ARf 


BIOLOGY 

LIBRARY 

G 


COPYRIGHT,  1901,  BY 
SHE   PRESIDENT   AND   FELLOWS  OF  HARVARD   COLLEGE 

ENTERED  AT  STATIONERS'  HALL,  LONDON. 

OUTLINES   OF   BOTANY 
W.   P.     TO 


PREFACE 


THE  present  text-book  has  been  prepared  to  meet  a  specific 
demand.  There  are  many  schools  which,  having  outgrown  certain 
now  antiquated  methods  of  teaching  botany,  find  the  best  of  the 
more  recent  text-books  too  difficult  and  comprehensive  for  practical 
use  in  an  elementary  course.  The  large  number  of  subjects  included 
in  the  modern  high  school  course  necessarily  confines  within  narrow 
time  limits  the  attention  which  can  be  devoted  to  any  one  branch. 
Thus,  more  than  ever  before,  a  careful  selection  and  judicious  ar- 
rangement as  well  as  great  simplicity  and  definiteness  in  presentation 
are  all  requisite  to  the  practical  success  of  any  one  course  of  study. 
This  book  offers  (1)  a  series  of  laboratory  exercises  in  the  morphology 
and  physiology  of  phanerogams,  (2)  directions  for  a  practicable  study 
of  typical  cryptogams,  representing  the  chief  groups  from  the  lowest 
to  the  highest,  and  (3)  a  substantial  body  of  information  regarding 
the  forms,  activities,  and  relationships  of  plants  and  supplementing 
the  laboratory  studies. 

The  practical  exercises  and  experiments  have  been  so  chosen  that 
schools  with  compound  microscopes  and  expensive  laboratory  appa- 
ratus may  have  ample  opportunity  to  employ  to  advantage  their 
superior  equipment.  On  the  other  hand,  the  needs  of  less  fortunate 
schools,  which  possess  as  yet  only  simple  microscopes  and  very  limited 
apparatus,  have  been  constantly  borne  in  mind.  Even  when  the 
cryptogams  and  certain  anatomical  features  of  the  phanerogams  are 
to  be  dealt  with,  much  may  be  accomplished  with  the  hand  lens,  and, 
where  applicable  at  all,  it  is  in  an  elementary  course  usually  a  better 
aid  to  clear  comprehension  of  objects  examined  than  the  compound 
microscope.  Furthermore,  the  experiments  covering  the  fundamental 
principles  of  plant  physiology  have  been  so  far  as  possible  arranged 
in  such  a  manner  as  to  require  only  simple  appliances. 

In  arranging  a  scientific  text-book  it  has  been  a  common  practice 
to  interpolate  directions  for  observation  and  experiment  in  the  body 
of  the  text.  In  teaching,  however,  the  writer  has  found  this  arrange- 
ment highly  objectionable.  Both  laboratory  work  and  class-room 
exercises  suffer  from  it.  Accordingly,  in  this  book  instructions  for 
laboratory  study  are  placed  in  divisions  by  themselves,  preceding  the 
related  chapters  of  descriptive  text.  The  pupil  with  his  book  open 
before  him  in  the  laboratory  will,  therefore,  not  here  be  confronted 
by  pictures  and  statements  constituting  keys  to  the  work  which  he 
should  carry  out  independently.  Although  it  is  not  intended  that 
each  laboratory  chapter  should  of  necessity  be  finished  before  the 
following  chapter  of  text  is  taken  up,  the  examination  of  the  plants 
themselves  should  naturally  be  kept  somewhat  in  advance  of  the 
recitations  which  summarize  and  complement  the  information  gained 
from  that  study. 

3 

195927 


4  PREFACE 

The  descriptive  text  follows  in  the  main  the  sequence  of  topics  of 
Gray's  "  Lessons  in  Botany,"  and  certain  parts  of  that  book  have  been 
retained,  as  occasional  paragraphs  will  show.  In  view  of  the  relation 
of  the  present  book  to  the  "  Lessons  "  as  indicated  on  the  title-page, 
the  writer  has  felt  free  to  adopt  the  phraseology  of  Dr.  Gray  wherever 
desired,  without  quotation  marks.  A  considerable  number  of  descrip- 
tive terms  and  definitions  applied  to  the  leaf  and  the  flower  have 
been  taken  from  the  "  Lessons,"  being  now  placed  apart,  for  the  use 
of  the  classes  making  a  somewhat  detailed  study  of  phanerogams  in 
a  systematic  way.  But  the  greater  part  of  the  descriptive  text 
throughout  is  new,  the  chapters  on  cryptogams  and  on  physiology 
being  entirely  so. 

In  an  endeavor  to  combine  the  best  features  of  newer  methods 
with  the  lucidity  and  defimteness  which  have  given  Dr.  Gray's  text- 
books their  extraordinary  merit,  the  present  book  departs  from  its 
predecessor  in  paying  more  attention  to  the  life  of  plants,  as  con- 
trasted with  mere  form.  The  writer  has  aimed  to  give  due  promi- 
nence to  function  which  underlies  form,  that  is  to  physiology  and  the 
relations  of  plants  to  their  surroundings.  Yet  while  seeking  properly 
to  emphasize  the  ecological  aspects  of  plant  life,  he  believes  that  ecol- 
ogy should  not  be  made  the  basis  of  elementary  botany.  It  seems  to 
him  that  a  course  should  be  built  primarily  upon  a  careful  study  of 
form,  leading  to  some  power  of  intelligent  discrimination  in  morphol- 
ogy and  of  accurate  description  in  the  technical  language  of  the 
science.  Equally  essential  are  certain  perfectly  definite  principles  of 
vegetable  physiology.  The  core  of  any  rational  elementary  course 
is  thus -believed  to  be  concrete,  embodied  in  precise  and  more  or  less 
technical  language,  and  measurably  endowed  with  a  quality  which 
some  would  with  disfavor  characterize  as  formalism.  The  writer  be- 
lieves that  the  body  of  concrete  instruction  is  not  likely  soon  to  be 
displaced  by  the  less  definite  and  as  yet  more  tentative  generalizations 
of  the  latest  Ecology. 

The  Appendix  is  an  essential  part  of  the  book,  but  is  primarily 
addressed  to  the  teacher.  It  contains  suggestions  in  regard  to  equip- 
ment, books,  materials,  experiments,  and  additional  exercises,  as  well 
as  pedagogical  methods. 

The  writer  appreciates,  and  here  takes  occasion  to  acknowledge, 
the  care  with  which  Mr.  C.  E.  Faxon  and  Mr.  F.  Schuyler  Mathews 
have  made  many  new  drawings  for  this  book.  Thanks  are  due  to  the 
staff  of  the  Gray  Herbarium  for  aid  in  proof  reading,  especially  to 
Miss  M.  A.  Day,  Librarian.  The  writer  is  deeply  indebted  for  advice 
and  criticism  to  Mr.  William  Orr,  Principal  of  the  High  School, 
Springfield,  Massachusetts.  Above  all,  the  writer  would  acknowledge 
his  great  obligation  to  Dr.  B.  L.  Robinson,  Asa  Gray  Professor  of 
Systematic  Botany  in  Harvard  University. 

R.    G.    LEAVITT. 


CONTENTS 


I.  LABORATORY  STUDIES  OF  SEEDS  AND  SEKDLINGS.  — Outline  of  the  prob- 
lem.   The  seed.    Exercise  I.,  The  embryo:  its  form  and  condition  previous 
to  germination.    Exercise  II.,  The  store  of  food.    The  seedling:  germina- 
tion.    Exercise  III.,  Vital  processes  in  germination:  experiments.    Exercise 
IV.,  Influence  of  temperature.    Exercise  V.,  Direction  of  growth  of  shoot 
and  root.      Exercise  VI.,  Development  of  the  seedling.      Supplementary 
topics.    Divisions  of  the  vegetable  kingdom.     The  course  of  study.    The 
members  of  a  complete  plant 7-14 

II.  SEEDS  AND  SEEDLINGS.  — Origin  of  the  seed.      The  embryo.      Store  of 
food.    The  resting  state.     Vitality.    Conditions  of  germination.    Develop- 
ment of  seedlings.    Root  hairs.    Chlorophyll        .  15-23 

III.  LABORATORY  STUDIES  OF  BUDS.  —  Exercise  VII.,  General  structure  of 
buds.     Exercise  VIII.,  Further  examples.    Exercise  IX.,  Number  and  posi- 
tion of  buds.    Exercise  X.,  Wintering  of  buds.     Exercise  XL,  Development, 
or  unfolding.    Exercise  XII.,  Non-development.    Exercise  XIII.,  Compara- 
tive vigor.    General  summary         .        .        .        .        .        »        .        .    23-27 

IV.  BUDS.  —  Growing  buds.      Resting  buds:    formation,  resting  condition, 
protection,  storage  of  food.     Non-development.    Adventitious  buds.    Defi- 
nite and  indefinite  annual  growth.     Forms  of  trees.    Supplementary  work  : 
ecology  of  buds     .',/»  ............    27-34 

V.  LABORATORY  STUDIES   OF  THE  ROOT.  —  Exercise   XIV.,  General  mor- 
phology and  gross  anatomy.    Exercise  XV.,  Roots  for  climbing.    Exercise 
XVI.,  Roots  for  storage.     Supplementary  subjects       ....    34,35 

VI.  THE  ROOT.  —  Origin.     Functions.    Action  of  root  hairs.    Growing  point. 
Root  cap.    Roots  of  epiphytes.     Of  parasites.    Roots  as  holdfasts.    Storage. 
Duration 36-45 

VII.  LABORATORY  STUDIES  OF  THE  STEM.  — Exercise  XVII.,  Characteristic 
external  features.      Exercise  XVIII.,  Internal  structure  (monocotyledons, 
dicotyledons).    Exercise  XIX.,  Structure  of  wood.    Exercise  XX.,  Ascent 
of  sap:  experiment.  Exercise  XXL,  Geotropism  :  experiments.  Heliotropism. 
Exercise  XXII.,  Special  uses  and  forms 45-51 

VIII.  THE  STEM.  —  Composition.     Growth.     Upright,  clambering,  climbing 
stems.    Organs  for  climbing.     Movement  of  tendrils.     Acaulescent  plants. 
Creeping  stems.     Vegetative  propagation  by  means  of  stems.     Stems  as 
foliage.    Longevity  of  trees.     Types  of  adaptation  :  xerophytes,  halophytes, 
hydrophytes,  mesophytes •        •        •        •    51-00 

IX.  LABORATORY  STUDIES  OF  THE  LEAF.  —Exercise  XXIII. ,  Activities  of 
the  leaf.     Experiments  on  assimilation,   respiration,  transpiration,  helio- 
tropism,  sleep  movements,  sensitiveness.     Exercise  XXIV.,  Parts  and  struc- 
ture of  the  leaf.    Experiments  on  conduction  and  turgidity.    Exercise  XXV., 
Leaf  of  the  Pea.     Exercise  XXVI.,  Venation.     Exercise  XXVIL,  Compound 
leaves.    Exercise  XXVIII.,  Special  uses  and  modifications          .        .    60-71 

X.  THK  T-.KAF.—  Offices.     Form  and  qualities.     Stipules.    The  petiole;   its 
uses  and  movements.      The  "  Sensitive   Plant."      The  blade.      Venation. 
Shape.    Influence  of  natural  surroundings.    Compounding.     Special  uses 
of  leaves.    Storage.     Scales.    Spines.     Leaves  for  climbing.     Tendril  leaf 
of  Cobaea.      The  "Sundew.      Pitcher  Plants.      Bladderwort.      Duration  OA 
leaves.    Defoliation.    Phyllotaxy.    Technical  terms  used  in  description. 


6  CONTENTS 

XI.  LABORATORY  STUDIES  OF  THE  FLOWER. — Exercise  XXIX.,  The  ovules 
and  ovary.     Exercise  XXX.,  The  pollen  and  stamen.     Exercise  XXXI. ,  The 
perianth.      Exercise    XXXil.,  Arrangement  of    floral   organs.      Exercise 
XXXIII.,    Inflorescence.       Exercise    XXXIV.,  The  flowers  of    Conifera. 
Further  work  on  the  flower 99-103 

XII.  THE  FLOWER.  —  General  morphology.     Ovules.     The  pistil.     Pistil  of 
the  gymnosperms.     Pollen.     Stamens.     Perianth.      Forms  of  corolla  and 
calyx.    Functions.     The   receptacle.    Floral   plan.      Morphological  nature 
of  floral  organs.     Suppression,  adnation,  coalescence.     Processes  leading  to 
formation  of  seed:  pollination,  fertilization.     Structure  of  the  pollen  grain. 
Cellular  structure  of  plants.     Growth  of  the  pollen  grain,  penetration  of 
pollen  tube,  fertilization.     Ecology  of  the  flower.     Self-  and  cross-fertiliza- 
tion.    The  former  often  prevented.     Agencies  and  adaptations  for  inter- 
crossing.     Wind,    water,    animals.       Cypripedium.      Salvia.      Milchella. 
Opening  and  closing  of  the  Catchfly.     Protection  of  nectar.     Grouping  of 
flowers.      Effect  of  crossing.      Supplementary   reading.      Supplementary 
studies :  field  work  on  ecology  of  the  flower.    Terminology  of  the  flower. 

103-143 

XIII.  LABORATORY   STUDIES   OF  THE   FRUIT. —  Exercise  XXXV.,  Floral 
organs  involved  in  the  fruit.     Exercise  XXXVI. ,  The  seed.    Outgrowths  of 
the  testa.    Exercise  XXXVIL,  The  fruit  in  relation  to  dissemination.  144-147 

XIV.  THE   FRUIT. — Nature  and  origin.     The  kinds.     Simple,  aggregate, 
accessory,  and  multiple  fruits.     Stone  and  dry  fruits.     Dehiscent  and  inde- 
hiscent  fruits.      Berry,  pome,   drupe,  achene,   caryopsis,  fig.      The  seed. 
Ecology  of  fruit  and  seed  as  regards  dissemination    ....     14 ('-150 

XV.  LABORATORY    STUDIES    OF    CRYPTOGAMS.  —  Nostoc.      Pleurococcus. 
Spirogyra.     Vaucheria.     Ectocarpus.     Rockweed.     Polysiphonia.     Nema- 
lion.      Bacteria.      Yeast.       Rhizopus.       Saprolegniacefe.      Peziza.     Micro- 
sphaera.     Toadstool.     Lichen.     Marchantia.     Moss.     Fern.     Selaginella. 
Lycopodiurn.     Equisetum 157-168 

XVI.  CRYPTOGAMS.  —  General  statement.     Blue-green  Algae :   characters  of 
the  group ;  Nostoc,  Oscillatoria.     Green  Algae  :  general  characters  ;  Pleuro- 
coccus, Ulothrix,  Spirogyra,  Vaucheria.      Brown  Algae :  general  characters, 
habitat,  etc.;  Ectocarpus  (Cutleria),  Rockweed.     Red  Algae:  characteris- 
tics, habitat ;  tetraspores  (Polysiphonia),  Nemalion.      General  summary  of 
reproduction  in    Algae.      Fungi:    general    statement;    Bacteria;    Yeasts; 
Bread  Mold;  Water  Mold;   Sac  Fungi,  Peziza,  Microsphaera,  Aspergillus ; 
Rusts;  Basidiomycetes,  Toadstool,  Clavaria,  Hydnum,  Polyporus.    Lichens. 
Liverworts  and  Mosses.     Marchantia.      Mosses.      Ferns  and  their  allies. 
Ferns.     Selaginella.     Other  Pteridophytes :    Lycopodium,  Equisetum.    Re- 
lationship of  Cryptogams  and  Phanerogams ;  the  transition  and  homologies. 

168-212 

XVII.  THE  MINUTE  ANATOMY  OF  FLOWERING  PLANTS. — Cellular  struc- 
ture.   The  cell:   protoplasm,  nucleus,  nuclear  division,  cytoplasm,  chloro- 
phyll bodies,  vacuoles,  sap  cavity.     Starch.      Protein  granules.    Calcium 
oxalate.     Multinuclear  cells.    Cell  wall  and  modifications.     Modified  cells. 
Wood  fibers.    Bast  fibers.     Collenchyma.     Grit  cells.    Cell  fusion.    Latex 
tubes.    Fibrovascular  bundles.     Structure  of  stems.      Structure  of  leaves. 
Structure  of  roots 212-229 

XVIII.  A  BRIEF  OUTLINE  OF  VEGETABLE  PHYSIOLOGY.  —  Constituents  of 
the  plant  body.     Sources  of  constituents.     Absorption  of  water;  of  nutrient 
salts.     Transfer  of  water.     Root  pressure.     Ascent  of  sap.     Transpiration. 
Carbon  assimilation.    Digestion.    Formation  of  albuminous  matter.     Trans- 
location  of  food.    Storage.    Respiration.    Resting  periods.    Growth :  phases, 
grand  period,  fluctuations,  conditions.     Movements,  spontaneous,  induced. 
Circumnutation.     Geotropism,  heliotropism,  hydrotropism.     Variations  of 
light  and  heat.     Change  of  turgidity.    Irritability   ....    229-240 

APPENDIX 241-259 

INDEX  AND  GLOSSARY 261-272 


OF  THE 

UNIVERSITY 

OF 


OUTLINES    OF   BOTANY 


I.  LABORATORY  STUDIES  OF  SEEDS  AND 
SEEDLINGS 

A  seed  comes  to  the  ground,  lodges  in  a  crevice  of  the 
earth,  is  warmed  by  the  sun  and  wet  by  the  rain,  and 
after  a  time  a  new  plant,  the  seedling,  appears. 

a.  To  what  extent  is  the  new  plant  already  formed 

within  the  seed  before  germination  begins  ? 

b.  What  provision  is  made  in  the  seed,  in  the  way  of 

food,  for  the  growth  of  the  seedling  and  its  estab- 
lishment as  an  independent  individual  ? 

c.  What  internal  processes  at  the  time  of  germination 

may  be  detected  by  suitable  experiments  ? 

d.  By  what  steps  does  the  nascent  plant  {embryo)  de- 

velop and  attain  to  a  life  of  self-support  ? 

These  are  the  general  questions  which  the  student  is 
asked  to  answer  for  himself  in  the  studies  outlined  in  this 
chapter.  The  first  exercises  deal  with  the  seed  before 
germination,  and  the  later  ones  with  the  seedling,  that  is, 
with  the  germination  of  the  embryo  and  subsequent 
events. 

THE   SEED 

EXERCISE  I.     THE  EMBRYO:   ITS  FORM  AND  CONDITION  PREVIOUS 

TO  GERMINATION 
<_ 
Castor  Bean.  —  Beginning  at  the  smaller  end  of  the  seed,  cut  away 

the  hard  outer  coat,  or  integument,  without  injuring  the  contents,  or 
kernel.  Run  the  point  of  a  knife  around  the  edge  of  the  kernel,  then 
split  the  halves  apart. 

7 


8  STUDIES   OF  SEEDS  AND   SEEDLINGS 

Carefully  remove  for  study  the  structures  discovered  within.  Exam- 
ine them  with  the  lens.  Describe  all  parts  of  the  kernel  with  included 
embryo. 

The  substance  surrounding  the  embryo  is  the  albumen;  the  leaves 
are  the  cotyledons ;  the  axis,  or  stemlet  upon  which  they  are  borne,  is 
the  caulicle. 

Draw :  (1)  The  embryo  separated  from  the  albumen  (  x  2).1  (2)  A 
longitudinal  section  of  the  kernel  cutting  the  cotyledons  in  halves  (  x  3). 

White  Lupine.  —  The  parts  all  become  visible  on  removing  the  seed 
coats  and  separating  the  well-marked  halves  of  the  seed.  Note  caulicle, 
cotyledons,  and  between  the  latter  a  third  part,  the  plumule,  of  several 
diminutive  members.  Compare  with  the  embryo  of  Castor  Bean, 
noting  striking  differences. 

Draw  the  embryo  with  one  cotyledon  removed,  so  as  to  show  the 
plumule  (x3). 

Indian  Corn.  —  Lying  just  beneath  the  surface  of  the  grain  is  a 
roughly  wedge-shaped  body.  Remove  this,  leaving  the  pasty  portion 
—  the  albumen.  In  one  face  is  a  cleft.  Pull  this  apart,  exposing 
structures  within. 

Study  the  embryo  now  in  hand.  A  longitudinal  section  will  help. 
In  order  to  identify  more  surely  the  members  of  the  embryo,  study 
also  a  sprouted  seed,  in  which  root  and  plumule  show  plainly.  The 
large  single  cotyledon  is  one  feature  to  be  especially  noted. 

Compare  and  correlate  all  its  different  portions  with  the  parts  of 
the  embryos  of  Castor  Bean  and  Lupine. 

Draw  surface  and  sectional  views  of  the  embryo  to  show  the 
structure  (x  3). 

From  the  examples  above  answer  the  question,  To  what  extent 
is  the  new  plant  already  formed  within  the  seed  before  germination 
begins  ? 

EXERCISE  II.     THE  PROVISION  OF  FOOD  DESIGNED  FOR  THE 
EARLIEST  GROWTH  OF  THE  YOUNG  PLANT 

1.  Where  is  the  nourishment  stored  ?  Answer  this  for  Castor  Bean, 
Lupine,  and  Indian  Corn.  In  addition,  examine  seeds  of  the  Four- 
o'clock,  and  others  provided  by  the  teacher. 

Longitudinal  sections  will  generally  show  at  once  the  location  of  the 
food  store,  whether  outside  the  embryo,  in  which  case  the  seed  is  said  to 
be  albuminous,  or  within  the  much  swollen  tissues  of  the  nascent  plant 
itself,  when  the  seed  is  called  exalbuminous,  or  lacking  in  albumen. 

Classify  the  seeds  studied  as  albuminous  or  exalbuminous. 

1  This  means  the  drawing  is  to  be  two  times  the  size  of  nature. 


STUDIES  OF  SEEDS  AND  SEEDLINGS        9 

In  the  Four-o'clock  remove  the  integuments,  and  separate  embryo 
and  albumen  carefully. 

Draw  the  food  mass  of  Four-o'clock.  Indicate  by  dotted  lines  the 
natural  position  of  the  embryo.  Use  the  hand  lens  (  x  3). 

2.  What  substances  constitute  the  food  of  the  seedling  ?  The  very 
numerous  substances  of  which  plants  are  composed  are  capable  of 
being  recognized  by  appropriate  tests.  A  test  consists  of  the  treat- 
ment of  the  tissues  with  certain  chemicals.  The  success  of  the  test 
depends  upon  observing  some  change  of  appearance,  as  of  color,  known 
to  be  due  to  the  action  of  the  chemical  employed  upon  the  substance 
for  which  search  is  being  made. 

Test  for  starch.  —  Treat  a  piece  of  laundry  starch  with  dilute  iodine. 
Note  the  color  imparted.  Starch  alone  receives  this  hue  from  this 
reagent.  Experiment  upon  the  seeds  supplied  in  order  to  determine 
which  contain  starch,  and  in  what  parts  the  starch,  if  found,  is  lodged. 
It  may  be  necessary  to  pulverize  or  boil  a  part  of  the  seed  in  some 
cases. 

A  second  food  material,  of  frequent  occurrence  in  seeds.  —  Crush  a 
whole  kernel  of  Castor  Bean.  If  this  is  done  with  the  fingers,  the 
characteristic  feeling  of  the  expressed  liquid  when  the  fingers  are 
rubbed  together  shows  the  nature  of  the  food  material  in  question. 
Seeds  of  Flax  and  of  Cotton  may  be  crushed  out  with  the  flat  of  a 
knife  blade  for  the  same  substance. 

Other  forms  of  reserve  food  matter.  — Several  of  these  are  not  readily 
discovered  without  chemical  tests  or  microscopic  examination.  But  a 
form  occurring  in  the  seeds  of  a  number  of  plants  of  considerable 
economic  importance  is  well  seen  in  the  date  seed.  Cut  the  "  stone  " 
of  a  date  in  halves  transversely.  Examine  with  the  hand  lens  the 
small  embryo  lying  crosswise  of  the  seed. 

Note  the  toughness  of  the  main  bulk  of  the  seed.  It  is  not  gritty, 
like  the  stone  of  a  cherry,  but  hornlike.  It  is  the  albumen,  dissolved 
during  germination  and  used  for  the  support  of  the  seedling. 

From  the  studies  in  Exercise  II  answer  the  question,  What  provi- 
sion is  made  in  the  seed,  in  the  way  of  food,  for  the  growth  of  the 
seedling  and  its  establishment  as  an  independent  individual? 

THE  SEEDLING.     GERMINATION 

EXERCISE  III.     WHAT  INTERNAL  PROCESSES  ARE  DISCOVERABLE 
AS  THE  EMBRYO  BEGINS  TO  GROW,  AND  GROWTH  PROGRESSES? 

Experiment  i.  —  Select  seedlings  of  Bean  in  the  first  stages  of  germi- 
nation, the  caulicles  coming  into  view.  Remove  the  seed  coats.  Drop 
a  dozen  of  the  denuded  beans  into  a  four-ounce  or  six-ounce  bottle 
filled  with  water  which  has  been  recently  boiled  to  drive  off  dissolved 
air,  and  allowed  to  cool. 


10       STUDIES  OF  SEEDS  AND  SEEDLINGS 

The  cork,  pierced  by  two  glass  tubes  that  penetrate  a  quarter  of  an 
inch  or  so  beyond  the  inner  surface,  should  be  put  in  with  care  to 
exclude  even  the  smallest  bubbles  of  air;  and  the  water  should  rise  to 
fill  the  tubes  completely  as  the  cork  is  pushed  in.  Place  the  fingers 
tightly  over  the  glass  tubes  and  invert  the  bottle.  Stand  it  mouth 
down  in  a  dish  of  water  (e.g.  a  tumbler).  Be  sure  no  air  is  present  in 
the  bottle. 

Displace  the  water  in  the  bottle  by  hydrogen  gas.  Lead  the  hydro- 
gen from  the  flask  into  the  bottle  only  after  all  air  has  been  driven 
off  in  the  flask.  Allow  the  apparatus  to  stand  as  now  adjusted  in 
some  situation  favorable  to  the  growth  of  the  beans. 

Beside  it  place  a  quite  similar  arrangement,  also  with  sprouted 
beans,  but  let  this  one  contain  air  in  place  of  hydrogen. 

Make  full  notes  of  the  preparation  and  conditions  of  this  experi- 
ment. Several  days  may  be  required  for  the  result  to  be  plainly 
seen.  Thereafter  finish  the  notes  on  the  experiment. 

In  this  exercise  hydrogen,  a  harmless  gas,  is  used  to  give  an 
atmosphere  devoid  of  oxygen.  The  second  jar,  filled  with  air,  has  of 
course  a  supply  of  the  latter  gas.  What  is  your  inference  concerning 
the  presence  of  oxygen? 

Experiment  2.  —  In  a  fruit  jar  one-third  full  of  sprouting  corn  place 
a  small  beaker  of  limewater.  Cover  the  jar  tightly.  Another  beaker 
with  like  contents  is  to  be  placed  in  an  empty  jar  beside  the  first,  and 
this  jar  likewise  closely  covered.  After  an  interval  of  from  one  to 
several  hours  observe  the  appearance  of  the  liquid  in  both  beakers. 
Note  any  difference. 

Take  a  small  beaker  of  fresh  limewater.  Breathe  gently  upon  it 
till  a  change  is  produced.  This  action  of  one's  breath  upon  limewater 
has  what  bearing  in  explaining  the  effect  observed  in  the  jar  of  sprout- 
ing corn?  What  is  the  object  of  the  second  jar  and  beaker? 

Experiments  1  and  2  will  enable  the  student  to  infer  — 

(1)  Whether  the  atmosphere  supplies  anything  more  than  moisture 
to  the  germinating  plant ;  (2)  Whether  the  plant  gives  back  anything 
into  the  atmosphere. 

What  action  necessary  to  the  life  of  animals  does  this  double  pro- 
cess in  growing  plants  resemble  ? 

Experiment  3.  —  Having  removed  the  beaker  from  the  jar  of  seed- 
lings used  in  the  previous  experiment,  tie  a  cloth  over  the  mouth  of 
the  jar.  Near  by  lay  a  thermometer.  When  the  mercury  column  has 
become  stationary,  note  the  reading  accurately  (without  handling  the 
bulb),  and  passing  the  instrument  through  a  small  hole  in  the  cloth, 
insert  its  bulb  amongst  the  seedlings. 

Within  five  or  ten  minutes  observe  with  exactness  the  temperature 
of  the  seedlings.  Is  it  higher  or  lower  than  that  of  the  room? 


STUDIES  OF  SEEDS  AND  SEEDLINGS       11 

The  jar  must  not  stand  in  direct  sunlight,  the  effect  of  which 
would  be  to  render  the  contents  wanner  than  the  room. 

It  would  be  well  to  find  by  means  of  another  thermometer  whether 
the  temperature  outside  the  jar  changes  in  the  same  direction  equally, 
during  the  time  of  observation. 

Is  there  any  connection  between  the  activity  of  the  seedlings, 
detected  by  Experiments  1  and  2,  and  their  heat  condition  indicated 
by  the  thermometer  in  Experiment  3  ? 

EXERCISE  IV.    INFLUENCE  OF  TEMPERATURE  ON  GERMINATION 

Experiment  4.  —  Take  100  seeds  of  Bean,  100  grains  of  Indian  Corn, 
and  100  grains  of  Wheat.  Soak  all  the  seeds  for  twenty-four  hours  in 
water.  Note  the  change  or  changes  produced. 

The  seeds  of  each  kind  are  then  to  be  divided  into  two  sets  of  50 
each.  Place  one  set  of  each  kind  in  a  suitable  receptacle,  where  they 
will  be  kept  moist,  but  not  covered  with  water  (e.g.  place  between 
layers  of  wet  blotting  paper,  or  in  moist  cotton,  or  in  wet  sphagnum 
moss,  the  receptacle  being  closed  to  prevent  evaporation).  Put  the 
receptacle  in  a  warm  place  where  the  temperature  will  be  as  nearly 
75°  Fahr.  as  possible.  Treat  the  other  sets  in  like  manner,  but  expose 
to  a  low  temperature  —  but,  of  course,  above  freezing.  Each  day 
record  in  a  table  the  number  of  seeds  of  each  kind  that  have 
sprouted.  What  is  your  inference  concerning  the  influence  of  tem- 
perature ? 

EXERCISE  V.    DIRECTION  OF  GROWTH  OF  PLUMULE  AND  ROOTLET 

Experiment  5.  —  By  a  chance  position  of  the  seed  in  the  soil  the  nas- 
cent root,  or  radicle,  on  emerging  may  have  its  tip  directed  toward  any 
point  but  the  right  one.  Ascertain  as  follows  how  an  inverted  seedling 
behaves.  Fit  a  double  roll  of  blotting  paper  into  a  beaker.  Moisten. 
Between  the  paper  and  the  glass  place  seedlings,  well  sprouted,  with 
the  roots  pointing  upward,  the  plumules  downward.  They  are  held 
in  place  by  the  pressure  of  the  paper.  But  if  some  of  the  seeds  are 
large,  —  like  the  Lupine,  —  tuck  wads  of  cotton  in  on  either  side  to 
support  the  radicle,  and  prevent  it  from  falling  or  bending  over. 

Pour  a  little  water  into  the  beaker.  This,  soaking  up  on  the  blot- 
ting paper,  will  keep  the  seedlings  moist.  Cover  the  beaker  to  pre- 
vent drying  up.  Draw  some  of  the  seedlings  well  enough  to  record 
their  positions.  After  two  or  three  days  examine  and  draw  again. 

Record  the  preparation  and  results  of  this  experiment.  Is  there 
indicated  anything  which  might  be  termed  sensitiveness,  together 
with  active  growth  toward  or  away  from  the  direction  of  gravity? 

Or  are  the  affected  parts  simply  bent  by  their  own  weight? 


12  STUDIES   OF  SEEDS  AND   SEEDLINGS 

EXERCISE  VI.     THE  DEVELOPMENT  OF  THE  SEEDLING 

Experiment  6.  —  An  exceedingly  important  change  undergone  by 
the  seedling  as  it  conies  out  of  the  soil  or  the  seed  into  the  light, 
may  easily  be  overlooked.  In  order  to  single  out  this  effect  from 
others  observed  in  the  course  of  the  young  plant's  development,  next 
to  be  studied,  germinate  some  seeds  in  the  dark,  and  let  the  seedlings 
develop  quite  away  from  the  influence  of  light.  Their  increase  of  size 
and  the  succession  of  parts  will  be  much  like  that  of  ordinary  seedlings, 
and  their  appearance  similar  except  in  the  one  vital  particular  —  a 
characteristic  of  plants  so  commonplace  that  it  is  hard  to  realize  its 
true  importance. 

In  the  course  of  the  studies  below  let  the  above  seedlings,  and  per- 
haps others  grown  in  very  dim  light,  be  compared  with  those  grown 
in  full  light. 

Turning  now  to  the  general  development  of  the  seedling,  the 
student  should  consider  afresh  that  in  the  buried  seed  there  is  a 
nascent  plant,  and  that  at  the  start  it  is  confronted  by  a  complicated 
problem.  In  many  cases  the  very  first  difficulty  is  how  to  escape  from 
the  wrappings  of  the  seed  itself.  After  that  there  is  the  question  how, 
through  growth  from  a  very  limited  food  supply,  on  the  one  hand  to 
reach  the  air  and  spread  a  small  crown  of  leaves,  and  on  the  other  to 
establish  connection  with  the  soil. 

Germinate  seeds  of  Squash,  Onion,  White  Lupine,  Pea,  and  Morn- 
ing Glory,  to  various  stages.  Write  notes  along  the  lines  indicated 
below,  and  illustrate  by  drawings. 

1.  Any  special  methods  of  getting  free  from  seed  coats. 

2.  Whether  the  cotyledons  are  raised  out  of  the  ground  or  not. 

3.  The  mode  of  extracting  cotyledons  or  plumule  from  the  soil. 

4.  AVhether  the  cotyledons  serve  as  food  sacs,  as  foliage  leaves,  or 
as  both. 

5.  In   which  cases  the  plumule  develops  early,   in  which   late ; 
reasons. 

6.  In  albuminous  seeds,  what  organ  of  the  embryo  acts  to  absorb 
the  albumen. 

On  points  calling  for  individual  judgment  rather  than  statement  of 
facts,  let  the  opinion  formed  by  the  pupil  be  expressed  distinctly  as 
such. 

Supplementary  Topics  for  Investigation  (optional) 

1.  The  rudimentary  embryos  of  orchids.     Material,  seeds  of  native 
or  greenhouse  plants.     Polyembryony  of  Spiranthes  cernua. 

2.  Embryos  of  certain  Conifers.     Pinus  Lambertiana,  P.pinea,  or 
even  smaller  seeded  species  for  the  seeds.     Larix  Americana  (Hack- 
matack) and  Picea  exceha  (Norway  Spruce)  for  germination. 


STUDIES    OF  SEEDS  AND   SEEDLINGS  13 

3.  The   dependence    of   seedlings   upon    the  nourishment  in   the 
cotyledons.     Compare  the   growth  of  entire  plantlets  with   that   of 
plantlets  deprived  of  one  or  both  cotyledons. 

4.  To  what  size  will  the  food  store  of  the  seed,  with  the  addition 
of  water  alone,  bring  the  seedling  ?     Exclude  light ;  for  in  darkness 
the  seedling  can  make  no  new  food.     Sprout  several  kinds  of  seeds, 
choosing  a  variety  as  regards  the  amount  of  albumen  or  size  of  the 
embryo.     Tie  mosquito  netting  loosely  over  the  mouth  of  a  dish,  and 
fill  the  dish  with  water  until  it  touches  the  netting,  upon  which  place 
the   sprouted  seeds  with   the  radicles  going  down  into  the  water. 
Report  the  results,  and  illustrate  with  the  plants  grown. 

Investigations  3  and  4  may  be  made  at  home. 

Divisions  of  the  Vegetable  Kingdom.     The  Course  of  Study 

One  has  but  to  draw  upon  his  everyday  observation  to 
realize  how  varied  is  the  plant  realm.  There  are  such 
diverse  types  as  the  trees  and  herbs  that  we  see  every- 
where about  us,  the  ferns,  the  mosses,  the  molds  and 
toadstools,  and  the  seaweeds.  These  differ  so  widely 
from  one  another  that  at  first  sight  there  seems  to  be 
little  upon  which  one  could  base  any  notion  of  a  common 
relationship. 

Nevertheless,  the  multitude  of  forms  have  been  brought 
together  into  comparatively  few  grand  divisions,  and  close 
study  has  revealed  a  considerable  measure  of  agreement 
running  through  the  whole  series.  We  may  reasonably 
suppose  that  all  plants  are  of  one  stock,  and  that  the 
higher  groups  have  sprung  from  forms  resembling  the 
lower. 

In  his  present  work  the  student  is  concerned  with  but 
one  type,  the  highest  of  all,  that  of  the  FLOWERING 
PLANTS,  or  PHANEROGAMS.  It  comprises  nearly  all 
the  plants  of  large  size,  and  by  far  the  greater  part 
of  those  which  are  useful  to  mankind  —  the  forests, 
the  grasses,  the  grains,  the  fruits,  the  fiber  plants,— 
those  that  at  present  make  the  earth  green  and  hab- 
itable. 

All  the  lower  plants  of  diverse  sorts,  from  the  ferns 
downward,  are  termed  FLOWERLESS  PLANTS,  or  CRYPTO- 
GAMS. They  are  reserved  for  the  latter  part  of  the  course. 


14  STUDIES   OF  SEEDS  AND   SEEDLINGS 

Phanerogams  and  Cryptogams  have  much  in  common, 
as  has  just  been  stated :  the  highest  Cryptogams  closely 
resemble  the  lowest  Phanerogams.  Yet  the  latter,  as  a 
whole,  form  a  well-marked  group  by  themselves.  One 
mark  of  distinction  may  be  stated  thus  :  — 

Phanerogamous  plants  grow  from  seed  and  bear  flowers 
destined  to  the  production  of  seed.  By  many  recent 
authorities  they  have  been  termed  Seed  Plants,  or  Sper- 
matophytes;  and  this  designation  is  more  significant  than 
the  earlier  and  commoner  one  of  flowering  plants. 

The  reproduction  of  Cryptogams  is  carried  on  by  means 
of  spores,  bodies  very  much  smaller  and  simpler  than  the 
smallest  and  most  rudimentary  seed.  The  spores  contain 
no  ready-formed  plants.  They  go  through  a  series  of 
changes,  quite  unlike  anything  to  be  observed  in  the 
germination  of  seeds,  before  the  form  of  the  plant  which 
gave  rise  to  them  is  reproduced.  The  pollen  of  flowering 
plants,  which  must  be  familiar  even  to  those  who  have 
paid  little  or  no  attention  to  plant  structure,  closely 
resembles  the  spores  of  the  floweiiess  plants.  This  may 
enable  one  to  see,  at  a  single  glance,  the  wide  difference 
between  spores  and  seeds. 


The  Members  of  a  Complete  Plant 

The  seedlings  studied  in  the  last  Exercise  were  com- 
plete plants.  They  were  provided  with  all  necessary 
organs  of  vegetation.  All  phanerogamous  plants  con- 
sist of  (1)  root,  and.  (2)  shoot ;  the  shoot  consisting  of 
(a)  stem,  and  (6)  leaf.  It  is  true  that  some  excep- 
tional plants,  in  maturity,  lack  leaves,  or  lack  roots. 
These  exceptions  are  few.  The  parts  of  the  phanerogams 
studied  are  to  be  assigned  to  root,  stem,  or  leaf.  Let 
it  be  understood  that  when  in  the  studies  on  flowering 
plants  the  question  is  asked,  "  What  is  the  mor*phology, 
or  nature,  of  this  part  ? "  this  is  equivalent  to  asking, 
"  Is  the  part  in  question  of  the  nature  of  root,  or  .of 
stem,  or  of  leaf?" 


SEEDS  AND   SEEDLINGS 


15 


1.  Central  portion  of  one 
of  the  flowers  of 
Hermannia  Tex- 
ana, showing  the 
seed  rudiments. 


Bud 


II.    SEEDS   AND   SEEDLINGS 

I.  The  seed  carries  within  it  a  minute  plant.  The  seed 
originates  in  the  flower,  within  an  often  globular  or  pod- 
like  structure  (Fig.  1),  which, 
though  generally  the  least 
conspicuous  of  the  floral 
organs,  may  have  attracted 
the  student's  attention  on 
account  of  its  central  posi- 
tion and  peculiar  form.  This 
receptacle  may  contain  a 
very  great  number  of  the 
rudiments  of  the  future 
seeds,  or  only  a  few,  or  even 
only  one  ;  and  may  be  the 


Seed  vessel 


2.  Buds,  flowers,  and  ripened  seed  vessels 
(fruit)  of  Hermannia  Texana. 


sole  seed-bearing  part,  or  one  of  several  in  the  same 
flower.  After  the  floral  leaves  with  their  wide  expanse 
and  bright  colors  have  performed  the  part  they  play  in 
the  life  of  the  flower,  and  have  fallen  away,  this  seed 
receptacle  enters  upon  a  new  period  of  its  history.  It 
grows,  often  vigorously,  and  through  alteration  of  form 


16 


SEEDS  AND   SEEDLINGS 


and  texture  approaches  nearer  and  nearer  to  its  final  con- 
dition of  fruit  (Figs.  2,  3). 

2.    The  seed  rudiments  meanwhile  undergo  fundamen- 
tal changes  :  the  embryonic  plants  are  formed,  seed  coats 


3.  a,  the  fruit,  or  matured  form  of  the  central  organ  of  the  flower 
(Fig.  1),  cut  across  to  show  the  seeds ;  6,  a  seed,  magnified  ;  c,  a 
section  of  the  seed ;  d,  the  embryo  removed  from  the  seed. 

develop,  fitted  to  secure  the  dispersal  of  the  seeds  far  and 
wide,  or  to  protect  the  embryo,  and  a  store  of  food  for 
rearing  the  young  plant  to  a  certain  stage  is  provided 
(Fig.  3). 

3.  At  length,  when  the  seed  is  fully  ready  for  its 
mission,  the  now  ripened  fruit  falls  to  the  ground  and 
decays,  liberating  the  seeds,  or  is  borne  away  by  currents 
of  wind  or  water,  or  by  animals.  Or,  remaining  on  its  stem, 
it  either  opens  (Fig.  3),  allowing  the  seeds  to  be  scattered 

by  a  variety  of  agencies,  or  in  a 
number  of  cases  bursts,  forcibly 
ejecting  the  seeds  from  their 
receptacle. 

4.    The  primitive  plant,   or  em- 
bryo, inclosed  in  the  seed,  may  be 
so  rudimentary  that  it  shows  not 
distinction  of  organs.    Such  a  case 
is  furnished  by  Orchids,  epiphyt-^ 
ic1  upon  trees  in  tropical  forests, 
•i.  Seed  of  an  Orchid,  with    Their  flowers  are  often  large ;  but 

loose,  buoyant  coat,  and      .,  ,  , 

a  rudimentary  embryo    the  extremely  numerous  seeds  are 
(magnified).  of   the   smallest   size,  and  of  the 

1  Epiphytes  grow  upon,  but  derive  no  sustenance  from,  other  plants. 
Parasites  live  at  the  expense  of  their  hosts. 


SEEDS  AND   SEEDLINGS 


17 


simplest  structure  throughout  (Fig.  4).  Floating  through 
the  air  like  chaff,  they  are  borne  to  situations  suited  to 
the  life  habit  of  these  plants.  The  very  much  reduced 
embryo  is  a  minute  rounded  body  with  no  sign  of  leaf 
and  stem  appearing  until  germination  has  considerably 
advanced. 

5.  But  every  well-developed  embryo  consists  essentially 
of  a  nascent  axis,  or  stem,  —  the  caulicle,  —  bearing  at  one 
end  a  leaf  or  leaves,  —  the  cotyledons,  —  while  from  the 
other  end  a  root  is  normally  to  be  produced  (Fig.  3,  d). 

6.  The  number  of  cotyledons.  —  Several  of  the  embryos 
examined  in  the  laboratory  were  dicotyledonous,  that  is, 
two-cotyledoned.     Plants  which  are  thus  similar  in  the 
plan  of  the  embryo,  agree  likewise  in  the  general  struc- 
ture of  their  stems,  leaves,  and  blossoms  ;  and  thus  form 
a  class,  named  from   their    cotyledons, 

the  DICOTYLEDONS. 

7.  Figure  5  represents  the  Pine  seed 
seen  in  section,  together  with  the  young 
tree  after  its  cotyledons  are  fully  ex- 
panded.    Of  these  there  are  several,  a 
case  which  is  much  less  usual,  but  con- 
stant in  the  various  kinds  of  Pine,  where 
in  some  species  the  cotyledons  number 
twelve,  or   even   more.     And  in    some 
other   Coniferce,  or    cone-bearing   trees, 
the  same  peculiarity  is  found.     The  em- 
bryo is  here  said  to  be  polycotyledonous. 

8.  The  term  monocotyledonous  denotes 
the  possession  of  but  a  single  cotyle- 
don.    This  condition  goes  along  with 

other  peculiarities  of  external  and  internal  structure,  and 
is  thus  characteristic  of  a  class  of  plants  —  exemplified  by 
the  true  Lilies  and  the  Grasses  —  called  the  MONOCOTYLE- 
DONS. 

9.  In  addition  to  the  parts  already  referred  to,  many 
embryos  show  in  miniature  one  or  two  lengths  of  the  stem 
which  is  to  carry  the  growth  of  the  plant  upward  above 

OUT.   OF  3OT.  2 


5.  Section  of  a  Pine 
seed;  seedling 
showing  6  coty- 
ledons. 


18 


SEEDS   AND   SEEDLINGS 


6.  Embryo  of  the  Yel- 
low Pond  Lily 
(magnified). 


the  cotyledons,  with  several  of  the  first  leaves  which  it 
will  bear  (Fig.  6).  This  bud  of  the  ascending  axis,  already 
developed  in  the  seed,  is  the  plumule. 
In  the  Bean  and  similar  strong  embryos 
the  leaves  of  the  plumule  are  already 
perfect  as  concerns  outline,  veining, 
and  so  on,  and  need  only  to  gain  green 
color  and  a  larger  size  to  become  use- 
ful to  the  seedling  as  foliage.  These 
plants,  therefore,  very  soon  after  coming  out  of  the 
ground  are  found  actively  acquiring  the  means  of  further 
growth,  while  still  using  nourishment 
inherited  from  the  parent  plant. 

10.  Food.  —  Along  with  the  incipient 
plant  is  sent  a  store  of  food  in  a  form 
easily  .  used,  with  which    its    start    in 

an  independent  ca- 
reer will  be  made. 
The  amount  is  as 
variable  as  the  size 
of  the  embryo  it- 
self. It  may  be 

relatively  very  large,  as  seen  in  the 
seed  of  Actsea  (Fig.  7).  In  Fig.  8 
the  embryo  is  relatively  larger  than 

the  mass  of   nutrient  material.      This 

example  prepares  us  for  the  condition 

seen  in  the   seed  of  many  families  of 

plants,  where    a   supply    of   nutriment 

separate  from  the  germ  itself  is  never 

developed  (Fig.  9). 

11.  Food    matter    external    to   >the 
embryo    is   termed    albumen,    or    endo- 
sperm, and  seeds  having  it  are  called  albuminous  seeds. 
Those  lacking  albumen  are  called  exalbuminous. 

12.  It  will  readily  be  seen  in  most  cases  that  embryos 
unfurnished  with  albumen  are  not  in   consequence   the 
worse  off,  for  they  are  of  larger  size  and  their  tissues  are 


8.  Seed  of  the  Purslane, 
in  section,  the  em- 
bryo surrounding 
the  reduced  albu- 
men (magnified). 


7.  Section  of  the  seed 
of  Actsea,  show- 
ing the  minute 
embryo  and  the 
relatively  abun- 
dant albumen 
(magnified). 


9.  Exalbuminous  seed 
of  Gynandrop- 
sis,  in  section 
(magnified) . 


SEEDS   AND   SEEDLINGS  19 

swollen  out  with  nutrient  substances.  This  is  the  arrange- 
ment in  seeds  like  the  Peanut,  Walnut,  and  Chestnut ; 
the  edible  kernel  is  really  a  rudimentary  plant. 

13.  The  seed  food  of  embryonic  plants  consists  chiefly 
of  starch,  fat,   sugar,  and  in   smaller   quantities  proteid 
substances ;    that  is,  substances  resembling  the  white  of 
egg  and  the  curd  of  milk.     Transformed  by  the  growing 
embryo   and  seedling  into   living   substance   and  frame- 
work, with  the  addition  of  water  alone,  these  concentrated 
formative  matters  may  enable  the  young  plant  to  grow  to 
Inany  times  the  size  of  the  original  seed. 

14.  The  resting   state.  —  The   germ   may  remain  long 
dormant  in  the  seed.     Its  condition  is  then  like  that  of 
the  buds  of  trees  and  the  underground  bulbs  of  herbaceous 
plants  in  winter.     Life  sleeps,  so  to  speak  ;  and  the  living 
parts  can  endure   extremes  of  dryness,   cold,  and  so  on, 
which  they  are  unable  to  bear  in  their  more  active  periods. 
Thus  the  embryo  passes  uninjured  through  change  of  sea- 
sons that  would  cause  the  death  of  a  seedling.     Dormant 
and  well  protected,  it  may  be  carried  to  great  distances. 
If  at  first  unfavorably  lodged,  the  seed  may  long  await  a 
change  of  circumstances.     When  a  forest  is  cleared  away, 
a  great  variety  of  field  plants  at  once  spring  up,  doubtless 
from  seed  deposited  in  the  soil  long  before. 

15.  Retention  of  vitality De  Candolle  kept  seeds  of 

many  kinds  for  fifteen  years,  when  those  of  a  few  species 
germinated.      In  another  case  the   known  age  of   seeds 
which  still  kept  their  vitality  was  forty-three  years.1     On 
the  other  hand,  certain  seeds  must  be  planted  as  soon  as 
separated  from  the  fruit. 

16.  The  conditions  of   germination.  —  When  the  slow 
inward   changes  of  the   dormant  period   have   fully  pre- 
pared the  seed,  —  or  when  ripeness  has  come,  even  without 
a  resting  stage,  —  germination  will  begin,  if  a  few  neces- 
sary   conditions    are    fulfilled.      There    must    be    water, 
warmth,  and   oxygen. 

1  The  stories  of  the  germination  of  seeds  from  mummy  cases  are  with- 
out foundation. 


20  SEEDS  AND   SEEDLINGS 

17.  Water.  —  Seeds  are  usually  rather  dry  on  issuing 
from   the   fruit.      Dryness   makes    the   seed   hardy.      In 
contact  with  water  therefore,  at  the  time  of  germination, 
they  often  swell  to  two  or  three  times  their  dry  volume. 
Actual  growth  in  plants,  too,  always  requires  much  water. 

18.  Warmth.  —  Moderate  heat  has  a  strong  influence  in 
hastening  germination.     For  Indian  Corn  and  Squash  the 
most  favorable  temperature  is  given  as  about  81°  Fahr. 
A  few  exceptional  seeds  will  sprout  at  the  freezing  point 
of  water.     Thus  seeds  of  a  Maple  have  been  germinated 
on  a  block  of  ice,  the  rootlets  penetrating  to  a  depth  of 
more  than  two  inches  into  the  dense,  clear  ice,  in  which 
they  melted  out  cylindrical  cavities  for  themselves.     Heat 
for  growth  is  here  generated  by  the  seedling  itself. 

19.  Oxygen  is  actively  inhaled  and  combines  with  the 
substances  of  the  embryo.    This  oxidation  furnishes  energy 
which  appears  in  growth  and  in  vital  heat ;  that  is,  in  heat 
in  the  seedling  similar  in  all  respects  to  the  bodily  warmth 
of  animals. 

20.  As  a  result  of  oxidation  carbonic  acid  gas  is  formed 
and  exhaled.     The  young  plant  thus  breathes  in  and  out. 
Respiration  is  common  to  all  living  things.     But  in  plants 
the  in-take  of  the  one  gas  and  the  out-going  of  the  other 
are  slow,  continuous,  and  imperceptible  processes. 

21.  The  development  of  seedlings.  —  If  one  looks  under 
the  White  Oak  in  late  autumn,  he  is  likely  to  find  that  the 
acorns  have  sprouted.    He  will  then  discover  that  many  of 
the  nuts,  if  lying  on  proper  surface,  for  instance  on  short- 
cropped  pasture  sward,  are  already  fast-bound  to  the  earth, 
the  radicles,  or  incipient  roots,  having  penetrated  the  soil. 
It  appears,  therefore,  that  seeds  may  germinate  and  attach 
themselves  without  being  covered  up  ;  though  a  covering 
of  some  sort,  as  sand,  soil,  or  dead  leaves,  is  advantageous, 
and  some  fruits,  or  their  carpels,  are  even  provided  with 
mechanical  contrivances  for  partially  burying  themselves.1 

22.  Suppose  that  a  seed  lies  thus,  like  the  acorn,  cleanly 
upon  the  surface,  and  that  it  has  been  drenched  by  rain 

1  See  Fig.  279. 


SEEDS  AND  SEEDLINGS 


21 


and  dew  until  germination  actually  begins.  Plainly  the 
first  need  in  this  case  is  a  root  developed  in  the  soil, 
whence  it  may  suck  up  the  water  and  other  substances 
required  for  the  con- 
tinued growth  of  the 
plantlet.  To  achieve 
this  object  the  caulicle 
is  pushed  out  of  the 
shell,  and  the  radicle  be- 
gins to  develop;  and  at 
once  it  may  be  seen  that 
the  elongating  axis  mani- 
fests something  very  like 
a  rudimentary  sense,  or 
a  number  of  senses.  It 
is  affected  by  outward 
influences.  The  radicle 
of  the  oak  is  found,  for 
instance,  to  have  been 
turned  sharply  down- 
ward; or  in  many  in- 
stances the  movement  of 
curvature  has  gone  still 
farther,  and  the  grow- 
ing radicle  has  followed 
the  under  surface  of  the 
shell  backward  to  the 
dampest  spot  in  the  im- 
mediate neighborhood  ;  namely,  the  place  where  the  acorn, 
resting  on  the  turf,  has  collected  a  little  of  the  moisture 
exhaling  from  the  earth  —  or  at  least  preserved  a  humid- 
ity higher  than  that  of  the  open.  Here  the  root  has  made 
another  turn,  under  the  combined  influence  of  gravity 
and  humidity,  and  has  entered  the  soil  (Fig.  10). 

23.  The  curving  movements  of  the  radicle  are  made  a 
little  way  back  of  the  tip,  and  the  growth  of  the  latter  is 
thereby  directed  toward  the  proper  surroundings. 

24.  Seedlings  from  buried  seed  come  into  the  air  by  a 


10.   Germination  of  the  White  Oak. 


UNIVERSITY 


SEEDS  J.ND  SEEDLINGS 

variety  of  methods.     When  the  cotyledons  are  designed 
to  act  in  the  sunlight  as  green  foliage  for  a  time,  they  are, 

in  general,  brought  out  of  the 
ground  by  the  lengthening  of  the 
caulicle.  As  it  grows,  this  usually 
bends  abruptly  just  below  the 
cotyledons;  and  the  top  of  the 
loop  thus  formed  is  seen  when 
the  cracking  of  the  soil  allows 
one  the  first  sight  of  the  springing 
seedling.  The  extraction  of  the 
leafy  parts  is  thus  managed  with 
the  least  danger  of  injury  from 
the  resistance  of  the  soil  (Fig.  11), 
and  at  the  same  time  the  seed 
coats  are  often  slipped  off. 

25.  The  main  part  of  the  origi- 
nal seed  may  remain  permanently 
buried,  while  the  nutrient  con- 
tents are  gradually  absorbed  and  carried  away  to  the 
actively  growing  regions  of  the  root  and  the  ascending 
shoot.  This  is  the  case  in  the  Horse-chestnut.  The  coty- 
ledons are  mere  reservoirs  of  food. 
Their  stalks  elongate  (see  Fig.  12), 
freeing  the  caulicle  and  plumule 
from  the  shell.  The  root  develops 
strongly,  and  the  plumule  rises, 
looped,  toward  the  surface. 

26.    The    end    of    the    root    for    a 
greater   or   less   length,  according  to 
the  size  of  the  plant,  is  always  elon- 
gating in  growth,  and  slipping  forward 
between  the  particles  of  soil,  which  it 
avoids  or  pushes  aside  as  the  occasion 
demands.     A  portion  just  behind  this  smooth  thrusting 
tip,  having  become  fixed  in  position,  throws  out  a  velvety 
coating  of  so-called  root  hairs.     These  penetrate  sidewise 
into  the  minutest  interspaces  of  the  soil,  and  adhere  to 


11.  Germination  of  the  Morn- 
ing Glory.  At  the 
left,  the  seedling  as  it 
appears  when  breaking 
from  the  soil ;  at  the 
right,  the  same  seedling 
a  little  later,  the  seed 
coats  thrown  off,  the 
stem  straightened,  and 
the  cotyledons  opened. 


12.  Germination  of  the 
Horse-chestnut. 


LABORATORY  STUDIES   OF  BUDS        .  23 

the  stony  particles.  Each  hair  is  a  microscopic  tube 
(Fig.  27),  out-growing  from  a  surface  cell,  and  serves  to 
conduct  water  and  draw  food  materials  into  the  tissues 
of  the  root,  whence  they  are  conveyed  to  the  leaves 
above. 

27.  Color.  —  The  embryo  in  the  seed  is  pale  or  color- 
less. The  seedling  —  except  the  root  —  is  dark  green, 
after  a  short  exposure  to  the  light.  But  if  the  seedling 
is  thrown  into  strong  alcohol,  this  newly  acquired  green 
color  is  extracted,  the  coloring  matter  proving  to  be  sepa- 
rable from  the  leaves  and  stems,  where  it  is  generated. 
It  is  a  definite  substance,  to  which  the  name  Chlorophyll 
has  been  given.  Without  this  substance,  plants  cannot  turn 
mineral  matters  of  scil  and  atmosphere  into  nourishment. 


III.    LABORATORY  STUDIES  OP  BUDS 

Buds  appear  as  conspicuous  features  on  most  of  the 
perennial  plants  of  temperate  and  cool  climates,  after  the 
autumnal  fall  of  leaves.  Such  winter  buds  are  to  be 
the  subjects  of  the  following  studies.1 

EXERCISE  VII.     THE  GENERAL  STRUCTURE  OF  BUDS 

Buds  of  the  following  common  species  will  show  what  winter  buds 
usually  contain,  in  what  a  compact  way  the  parts  are  pressed  together, 
and  how  some  parts  are  shielded  by  others. 

Lilac.  —  View  the  bud  endwise.  What  is  the  arrangement  of  the 
scales?  How  were  the  leaves  arranged  on  the  twig? 

Remove  the  scales  and  little  leaves  one  after  another,  laying  them 
down  in  the  order  of  removal.  Note  a  gradual  change  in  the  outlines. 
From  the  last-removed  members  it  is  easy  to  see  the  morphology  of 
all  the  parts,  including  the  scales.  What  are  the  scales  ?  Cut  a  longi- 
tudinal section.  Use  the  lens.  All  parts  are  seen  in  position  and 
proper  attachment. 

Draw  :  (1)  An  outer,  a  transitional,  and  an  inner  member,  as  taken 
off  (x  3.).  (2)  A  longitudinal  section  (x  10).  Label  all  parts. 

1  The  parts  of  the  leaf  — blade,  petiole,  and  stipules  —  should  be 
shown  on  the  board  to  the  class. 


24  LABORATORY  STUDIES   OF  BUDS 

Horse-chestnut.  —  Note  the  arrangement  of  the  scales.  Of  the  leaf 
scars  on  the  twig. 

Remove  the  scales  by  cutting  at  the  base.  Separate  the  wool- 
covered  members  within  and  remove  them,  counting  and  noting  down 
the  number  of  pairs.  Holding  one  of  these  parts  by  its  stalk,  scrape 
off  much  of  the  wool,  first  from  the  back,  then  from  between  the  leaf- 
lets. 

Cut  longitudinally  down  through  the  bud  core,  or  axis,  after  remov- 
ing all  scales  and  leaves.  With  the  lens  notice  the  short,  narrow, 
conical  part  upon  which  the  leaves  proper,  not  the  scales,  were  inserted. 
How  many  internodes l  in  this  bud  axis  ?  (Refer  to  the  number  of 
pairs  of  leaves  removed.)  How  many  internodes  in  the  last  season's 
growth  on  the  same  twig?  Does  the  bud  contain  an  ordinary  year's 
growth,  as  to  number  of  internodes  and  leaves? 

Draw:  The  bud  entire  (x  2).  One  of  the  young  leaves,  spread 
out  (x  3). 

Witch-hazel.2  —  Note  the  surface  of  the  bud  leaves.  Scrape.  Use 
the  lens.  Beneath  the  exterior  coating  is  the  leaf  soft,  green,  and 
apparently  alive,  or  leathery  and  dead  ?  Pull  the  bud  to  pieces.  Are 
any  parts  different  from  the  outer  leaves  ?  The  latter,  as  well  as  the 
inner  ones,  finally  develop  into  foliage  leaves.  There  are  no  scales. 
Such  buds  are  termed  naked  buds.  Draw  the  bud  entire  (x  2). 

EXERCISE  VIII. 

The  Tulip  Tree  (Liriodendron).  —  Note  the  flattish  form  of  the  bud  ; 
the  nearly  round  scar  near  the  base.  Separate  the  two  exterior  scales 
at  the  tip,  and  pull  them  off.  Relatively  to  the  little  leaf  now  seen, 
in  what  position  does  the  next  pair  of  scales  stand?  Examine  all  re- 
maining parts.  What  is  the  round  scar  at  the  base  of  the  outer  pair 
of  scales?  What  is  the  morphology  of  the  scales? 

Draw  the  bud  after  removal  of  the  outer  envelop. 

Magnolia.  —  Does  the  caplike  covering  of  the  bud  consist  of  two 
parts  fused  in  growth,  or  is  it  single?  What  is  the  small  scar  at  one 
side  of  the  bud?  Examine  the  contents  of  the  bud.  What  is  the 
morphology  of  the  bud  cap?  Draw  the  bud,  showing  the  scar. 

ADDITIONAL  STUDIES 

Make  a  study  of  several  other  buds  as  directed  by  the  teacher. 
Among  these,  the  buds  of  Mountain  Ash  (Pyrus  Americana  or  P. 
Aucuparia),  Green  Brier  (Smilax  rotund  i folia),  Mullein,  Dandelion,  and 
some  subterranean  bud  like  those  of  Smilacina,  Trillium,  Sanguinaria, 
or  Uvularia,  are  suggested. 

1  Interspaces  between  leaves.         2  For  alternative  material,  see  Appendix. 


LABORATORY  STUDIES   OF  BUDS  25 


EXERCISE  IX.     THE  NUMBER  AND  POSITION  OF  THE  BUDS 

The  position  of  buds  in  general,  with  reference  to  the  leaves  of  the 
previous  season,  must  have  already  attracted  attention.  What  is  that 
position?  When  two  or  more  buds  occur  together  they  have,  rela- 
tively to  one  another,  one  of  two  characteristic  arrangements,  as  seen 
in  the  following  species. 

Red  Maple.  —  How  many  buds  in  a  group?  Which  ones  maybe 
termed  extra,  or  accessory  ? 

Draw  enough  of  the  twig  to  show  the  essential  relations  of  the  buds, 
both  to  the  leaf  scar  and  to  one  another. 

Pipevine.  —  Examine  the  neighborhood  of  the  leaf  scar  with  the 
lens.  Cut  a  longitudinal  section  of  the  stem  through  the  middle  of 
the  scar.  Examine  the  cut  surfaces  of  the  bark.  Growing  points, 
distinguished  by  superior  greenness,  can  be  made  out.  Note  their 
number  and  relative  position. 

Make  a  drawing  (enlarged)  to  show  the  disposition  of  accessory 
buds  here  found. 

EXERCISE  X.     THE  WINTERING  OF  THE  YOUNG  SHOOT 

Refer  to  the  records  and  drawings  made  in  the  laboratory  for  the 
materials  of  a  comparative  account  of  buds,  with  reference  to  their, 
adaptations  to  winter  conditions.  Protection  against  sudden  chilling 
is  sometimes  perfect;  in  other  cases  temperature  seerns  to  be  disre- 
garded. Arrange  the  various  modes  of  meeting  the  dangers  of  cold 
in  an  orderly  manner  in  your  account. 

Are  there  any  other  sources  of  destruction  besides  low  temperature? 
If  so,  what?  And  are  buds  protected  against  these  dangers? 

EXERCISE  XL     THE  DEVELOPMENT  OR  UNFOLDING  OF  BUDS  1 

The  Lilac,  forced  to  grow  indoors,  may  be  studied.  Determine 
what  parts  have  grown  since  the  bud  came  out  of  the  typical  winter 
state.  Have  all  grown  equally ?  Have  some  not  grown? 

Draw  enough  to  show  what  happens  to  the  different  members  of 
the  winter  bud. 

If  possible,  compare  with  the  Lilac  the  unfolding  buds  of  two  other 
species,  as  the  Buttonwood  and  the  Sycamore  Maple. 

EXERCISE  XII.     THE  NOXDEVELOPMENT  OF  BUDS 

Select  a  branch  of  the  Horse-chestnut  five  years  old,  or  thereabouts. 
Count  the  total  number  of  leaf  scars.  Of  these,  how  many  now  sub- 
tend buds,  or  have  subtended  buds?  In  how  many  cases  have  buds 
developed  into  branches  or  flower  clusters? 

1  This  may  be  a  home  experiment. 


26 


LABORATORY  STUDIES   OF  BUDS 


Add  the  ages  of  all  the  existing  buds,  individually.  Then  divide 
this  total  by  the  whole  number  of  buds.  This  gives  the  average  age 
of  the  buds.  How  old  is  the  oldest  bud  on  the  branch?  Cut  some  of 
the  oldest  ones  open.  Should  you  judge  them  to  be  still  capable  of 
development,  in  case  of  need? 

Record  in  your  notes  all  numbers  and  ages. 


EXERCISE  XIII.     COMPARATIVE  VIGOR  OF  DEVELOPMENT 

Select  a  lateral  branch  of  the  Maple  provided,  showing  a  few  years' 
growth.  Hold  the  branch  in  the  position  in  which  it  grew.  Certain 
of  the  leaf  scars  now  look  upward,  part  of  them  to  right  or  left  (hori- 
zontally), and  part  toward  the  earth.  That  is,  there  are  two  sets, 
the  vertical  (above  and  below)  and  the  horizontal.  In  each  set  count 
the  whole  number  of  pairs  of  leaf  scars ;  also  the  number  (pairs) 
where  the  buds  have  made  some  growth. 

Record  in  a  table  like  the  following  :  — 


HORIZONTAL 

VERTICAL 

Whole    number    (pairs) 
Number,  where  buds  de- 
velop to  twigs 

Whole    number    (pairs) 
Number,  with  twigs 

Measure  roughly  the  combined  length  of  all  the  horizontal  twigs 
developed  from  lateral  buds.  Combined  length  of  vertical  twigs. 
Compare  the  numbers  obtained  thus  :  — 

Total  length  of  all  horizontal  twigs 

Total  length  of  all  vertical  twigs 

Count  the  whole  number  of  present  winter  buds  on  all  the  twigs  of 
each  set  separately.     This  gives  a  hint  as  to  their  comparative  vigor. 
Record  thus :  — 


Buds  on  horizontal  twigs 
Buds  on  vertical  twigs    . 


Is  there  any  advantage  to  the  tree  in  the  superior  development  of 
one  system  over  the  other? 

This  exercise  is  intended  to  bring  out  two  facts:  first,  that  certain 
buds  are  more  likely  to  develop  than  others ;  second,  that  certain  buds 
develop  more  vigorously  than  others.  The  exercise  is  not  intended  to 
teach  —  what  would  not  be  universally  true  —  that  the  horizontally 
directed  buds,  for  example,  are  always  more  vigorous  than  vertically 
directed  buds  ;  or  vice  versa. 


SUDS  27 

General  summary.  —  The  pupil  should  by  this  time  be 
self-informed  as  to  — 

a.  What  a  bud,  as  a  whole,  is. 

b.  What  the  reason  for  its  formation  is. 

c.  What  rudiments  of  future  growth  are  present. 

d.  How  nearly  these  approach  the  full-grown  condition 
as  to  form. 

e.  What  parts  are  of  merely  temporary  use. 
/.    What  the  morphology  of  these  parts  is. 

Make  a  brief  statement  covering  these  points,  by  way  of 
summary  of  the  work  on  buds. 

For  Supplementary  Work,  see  the  end  of  Chapter  IV.,  where  sugges- 
tions for  outdoor  and  indoor  observations  are  made. 


IV.   BUDS 
GROWING  BUDS 

28.  In  actively  growing  herbs  the  tip  of  the  stem  and 
the  rudiments  of  the  coming  leaves  —  appearing  at  first  as 
small  prominences  close  to  the  apex  —  are  usually  pro- 
tected from  accidents.  Bites  of  insects  or  other  animals, 
and  extremes  of 
heat,  light,  dry- 
ness,  and  cold,  are 
guarded  against  by 
the  nidturer  leaves 
standing  together 
over  the  younger 
parts  (Figs.  13, 14), 

or  bv  Special  COVer-      13-  Terminal  portion  of  a  shoot  of  Coleus;  young 
J     *,  leaves  shielding  the  growing  tip. 

ings.     The  forming 

members  of  the  Begonia  shoot  are  sheathed  by  a  pair 
of  scalelike  appendages  —  stipules  —  at  the  base  of  the 
highest  full  leaf  (Fig.  15).  In  addition,  in  this  plant, 
the  hot  rays  of  the  sun  are  in  nature  fended  off  by  the 
leaves  themselves,  which  are  raised  umbrellalike  over  the 


28  SUDS 

/ 

growing    point  ;    a   mode    of   protection    quite    perfectly 

represented,  also,  by  the   Castor   Bean   plant   (Fig.   16). 
In  the  Mullein,  protection  is  assured  both  in  the  growing 


14.  End  of  the  stem,  and  two  nas- 
cent leaves,  in  Coleus,  after 
removal  of  several  pairs  of 
the  leaves  of  the  growing 
bud. 


15.   Protection  of  the  growing  bud  of 
Begonia. 


season  and  in  winter  by  a  thick,  woolly  covering  of  plant 
hairs,  or  trichomes.  These  are  produced  by  all  the  leaves 
in  their  earliest  stages  when  crowded  together  in  the  bud, 


16.   Protection  of  the  terminal  bud  in  the  Castor  Bean. 

and  persist  when  the  leaves  are  mature.  The  tender 
sprouts  of  many  plants  are  well  supplied  with  trichomes 
of  a  special  kind,  secreting  distasteful  liquids  which  dis- 
courage the  attacks  of  herbivorous  insects. 


BUDS 


29 


.   Buds  of  the 
Hickory. 

Sometimes 


RESTING  BUDS 

29.   The  most  conspicuous  buds  are  the  scaly  resting 
buds   of   most    trees    and   shrubs   of    temperate   or   cold 
climates.      When  these  are  formed  at  the 
end  of  a  stem  or  branch,  they  are  referred 
to  as  terminal  buds.     In  the  angle,  or  axil, 

of  nearly  all  the  leaves 

others  are  found,  termed 

axillary  or  lateral  buds 

(Fig.  17). 

30.  Accessory   or    su- 
pernumerary     buds.  — 
There   are  cases  where 
two,     three,     or     more 
buds    spring   from    the 
axil   of   a   leaf,   instead 
of  the  single  one  which 
is  ordinarily  found  there. 

they  are  placed  one  over  the  other,  as 
in  the  Aristolochia,  or  Pipevine ;  and 
in  -  Pterocarya  (Fig.  18),  where  the 
upper  bud  is  a  good  way  out  of  the 
axil.  In  other  cases  three  buds  stand 
side  by  side  in  the  axil,  as  in  the  Red 
Maple. 

31.  Formation    of     winter    buds. — 
Such  plants  as  prepare  for  winter  by 
the   production   of   winter  buds  form 
them  early  in  the  foregoing  summer. 
In    many   woody   plants   the    axillary 
buds    do    not    show   themselves    until 
spring- ;  but  if  searched  for,  they  may 

18.  The  accessory  buds  5  ;  n        - 

of     Pterocarya    be    detected,    though    of    small    size, 

EhoifoKa,  some-    hidden  under  the  bark.       Sometimes, 
what  above   the 

axil,  and  already    though    early    formed,   they   may   be 
partially    devel-    collceaie(i  au  summer  long  under  the 

oped  in  the  nrst  ° 

summer.  base  of  the  leaf  stalk,  which  is  then 


30 


BUDS 


hollowed  out  into  a  sort  of  inverted  cup,  as  in  the  Button- 
wood,  or  Plane  Tree 
(Fig.  19). 

32.  Large  and 
strong  buds,  like 
those  of  the  Horse- 
chestnut  and  Hick- 
•  ory,  contain  besides 
the  scales  several 
leaves  or  pairs  of 
leaves,  ready  formed, 
folded,  and  packed  away  in  small  compass,  just  as  the 
seed  leaves  of  a  strong  embryo  are  folded  away  in  the 
seed  ;  they  may  even  contain  all  the  blossoms  of  the  ensu- 
ing season  plainly  visible  as  small  buds.  Buds  containing 


19.   Sub-petiolar  bud  of  the  Plane  Tree. 


20.  UndergroT-nd  stem  (**),  thickened  roots  (rf),  and 
resting  bud  of  Bell  wort  (Uvularia). 

both  leaves  and  flowers  are  termed  mixed  buds.  Under 
the  surface  of  the  soil,  too,  or  on  it,  covered  with  the  dead 
leaves  of  autumn,  similar  strong  buds  of  our  perennial 
herbs  may  be  found  (Fig.  20). 

33.  The  resting  state. — Buds,  like  seeds,  remain  in  a 
state  of  rest,  or  dormancy,  during  the  winter,  although 
life  is  hardly  reduced  to  such  low  terms  in  buds  as  it  is  in 
seeds.  Buds  are  therefore  more  easily  aroused  to  activity; 


SUDS 


31 


and  they  are  less  hardy.  Yet  in  the  coldest  weather  buds 
are  frozen  without  injury,  providing  the  freezing  and  sub- 
sequent thawing  are  not  too  sudden. 
Some  buds  which  will  grow  and  unfold 
when  placed  in  water  in  the  latter 
part  of  the  winter,  refuse  to  open  at 
an  earlier  period,  behaving  like  those 
seeds  that  will  germinate  only  after 
a  definite  length  of  time. 

34.  Protection.  —  The     means    and 
the  degree  of  protection  are  various. 
Against  sudden  changes  of  tempera- 
ture  thick,  woolly   covering   is   often 
provided,    growing    from    the    young 
leaves  and  around   their   bases.      To 
this    several    thicknesses   of   scales  — 

modified  leaves  — 
may  be  added.  The 
scales  usually  fall 
away  soon  after  the 
bud  bursts  open  in 
spring  ;  but  in  many 
instances,  like  the 
Buckeye  (Fig.  21), 
make  a  little  growth  toward  foliage.  In 
Pterocarya  (Fig.  22)  the  younger  leaves 
are  shielded  only  by  the  somewhat  broad- 
ened stalks  of  the 
partly  developed  out- 
er ones.  When  the 
latter  become,  in  the  spring,  the  full 
leaves  of  the  season,  such  buds  are 
termed  naked  buds,  i.e.  without  spe- 
cialized protective  scales. 

35.  The    slender,    pointed    axillary 
buds  of   the    Horse  Brier,    or   Green 
Brier,  lie  in  the  groove  of  the  petiole 
of  the  subtending  leaf,  and  are  partly 


21.  Development  of  the 
parts  of  the  bud 
in  the  Buckeye. 


22.  Naked  bud   of 
Pterocarya 
fraxinifolia. 


23.  Remains  of  the 
petiole  protect- 
ing the  bud  in 
Horse  Brier. 


32 


BUDS 


covered  by  the  margins  of  the  groove.  When  the  leaf 
falls  off  in  autumn,  the  base  remains  as  protection  to 
the  bud  (Fig.  23). 

36.  Store  of  food.  —  In  trees,  the  stems  which  bear  the 
buds  are  filled  with  abundant  nourishment  deposited  the 
summer  before  in  the  wood  and  in  the  bark.     Subterranean 
buds  are  supplied  from  thick  roots,  root  stocks,  or  tubers, 
charged  with  a  great  store  of  nourishment  for  their  use. 
(See  Figs.  20,  47,  48.) 

37.  Renewal  of  growth.  —  We  see  that  the  on-coming 
of  spring  finds  plants  ready  to  resume  their  interrupted 
activities,  since  new  shoots  are  complete  in  the  buds,  and 
food  is  at  hand  for  their  development.     As  soon  as  the 
tide   of  warmth  has  fairly  set  in,   therefore,   vegetation 
pushes  forth  vigorous^  from  such  buds,  and  clothes  the 
bare  and  lately  frozen  surface  of  the  soil,  as  well  as  the 
naked  boughs  of  trees,  with  a  covering  of  green,  and  often 
with  brilliant  blossoms.     Only  a  small  part,  and  none  of 
the  earliest,  of  this  vegetation  comes  from  seed. 

38.  Nondevelopment  of  buds.  —  It  never 
happens  that  all  the  buds  grow.  If  they 
did,  there  might  be  as  many  branches  in 
any  year  as  there  were  leaves  the  year 
before.  And  of  those  which  do  begin  to 
grow,  a  large  portion  perish,  sooner  or  later, 
for  want  of  nourishment  or  for  want  of 
light.  In  the  Hickory  (Fig.  17),  and  most 
other  trees  with  large  scaly  buds,  the  ter- 
minal bud  is  the  strongest,  and  has  the 
advantage  in  growth  ;  and  next  in  strength 
are  the  upper  axillary  buds ;  while  the  for- 
mer continues  the  shoot  of  the  last  year, 
some  of  the  latter  give  rise  to  branches, 
and  the  rest  fail  to  grow.  In  the  Lilac 
(Fig.  24),  the  uppermost  axillary  buds  are 
stronger  than  the  lower ;  but  the  terminal 
bud  rarely  appears  at  all;  in  its  place  the 
uppermost  pair  of  axillary  buds  grow,  and  so  each  stem  branches  every 
year  into  two,  —  making  a  repeatedly  two-forked  ramification. 

39.   Latent   buds.  —  Axillary  buds  that  do  not  grow  at  the  proper 
season,  and  especially  those  which  make  no  appearance  externalLv, 


24.   Buds  and  branching  of 
Lilac. 


BUDS  33 

may  long  remain  latent,  and  at  length  upon  a  favorable  occasion  start 
into  growth,  so  forming  branches  apparently  out  of  place  as  they  are 
out  of  time.  The  new  shoots  seen  springing  directly  out  of  large 
stems  may  sometimes  originate  from  such  latent  buds,  which  have 
preserved  their  life  for  years.  But  commonly  these  arise  from 

40.  Adventitious  Buds.  — These  are  buds  which  certain  shrubs  and 
trees  produce  anywhere  on  the  surface  of  the  stem,  especially  where 
it  has  been  injured.     They  give  rise  to  the  slender  twigs  which  often 
feather   the   sides  of  great  branches  of  our  American   Elm.     They 
sometimes  form  on  the  root,  which  naturally  is  destitute  of  buds; 
they  are  found  even  upon  some  leaves ;  and  they  are  sure  to  appear 
on  the  trunks  and  roots  of  Willows,  Poplars,  and  Chestnuts,  when 
these  are  wounded  or  mutilated. 

41.  Definite  annual  growth  from  winter  buds  is  marked  in  most 
of  the  shoots  from  strong  buds,  such  as  those  of  the  Horse-chestnut 
and    Hickory.      Sucli   a  bud   generally  contains,   already  formed  in 
miniature,  all  or  a  great  part  of  the  leaves  and  joints  of  stem  it  is  to 
produce,  makes  its  whole  growth  in  length  in  the  course  of  a  few 
weeks,  or  sometimes  even  in  a  few  days,  and  then  forms  and  ripens 
its  buds  for  the  next  year's  similar  growth. 

42.  Indefinite 'annual  growth,  on  the  other  hand,  is  well  marked 
in  such  trees  or  shrubs  as  the  Sumac,  and  in  sterile  shoots  of  the  Rose, 
Blackberry,  and  Raspberry.     That  is,  these  shoots  are  apt  to  grow  all 
summer  long,  until  stopped  by  the  frosts  of  autumn  or  some  other 
cause.     Such  stems  commonly  die  back  from  the  top  in  winter,  and 
the  growth  of  the  succeeding  year  takes  place  mainly  from  the  lower 
axillary  buds. 

43.  Forms  of  trees  determined  by  the  development  of  the  buds. — 
The  main  stem  of  Firs  and  Spruces,  unless  destroyed  by  some  injury, 
is  carried  on  in  a  direct  line  throughout  the  whole  growth  of  the  tree, 
by  the  development  year  after  year  of  a  terminal  bud :  this  forms  a 
single,  uninterrupted  shaft,  —  an   excurrent  trunk,  which  cannot  be 
confounded  with  the  branches  that  proceed  from  it.     Of  such  spiry  or 
spire-sltaped  trees,  the  Firs  or  Spruces  are  characteristic  and  familiar 
examples. 

44.  On  the  other  hand,  when  the  terminal  bud  fails  to  take  the 
lead  regularly,  there  is  no  single  main  stem,  but  the  trunk  is  soon  lost 
in  its  branches.     Trees  so  formed  commonly  have  rounded  or  spread- 
ing tops.     The  American  Elm  is  a  good  illustration  of  this  type,  in 
which  the  stem  is  said  to  be  deliquescent. 

Supplementary  Work.    Ecology  of  Buds 

The  following  outline  is  meant  to  suggest  some  lines  of  individual  research 
that  may  be  followed  throughout  the  year  in  any  place  where  plants  grow. 
Notes  made  from  nature  will  not,  of  course,  follow  this  scheme ;  for  such  a 
OUT.  OF  HOT.  — 3 


34  LABORATORY  STUDIES   OF  THE  ROOT 

summary  could  come  only  after  a  good  deal  of  looking  into  particular  cases. 
Observations  should  be  numbered  in  the  notebooks;  and  specimen  parts  of 
the  plants  whose  buds  are  described  should  be  kept  properly  numbered,  for 
determining  with  certainty  what  the  plants  are  that  have  been  studied.  There 
are  several  popular  works  from  which  the  names  of  plants  in  flower,  or  of  trees 
even  not  in  flower,  may  be  made  out  to  some  extent.  If  one  learns  the  use 
of  the  Manual,  names  may  be  determined  without  other  help.  Assistance 
may  often  be  had  from  a  trained  botanist  through  correspondence,  if  none  is 
available  near  at  hand. 

I.  Summer.    Growing  buds.    Protection  of  the  tender  tips :  against  (a)  in- 
sects, (b)  snails  (water  plants  and  low  wider-herbs),  (c)  any  ot hef  animals  ? 
(d)  excessive  light,  heat,  and  drying;  by  means  of  (a)  stipules,  (b)  petioles 
of  older  leaves,  (c)  trichomes,  (d)  convergence  and  overshading  by  all  the 
parts  generally,  (e)  other  arrangements. 

II.  Summer,  fall,  and  winter.     Resting  (or  "winter")  buds.    A.  When 
are  they  formed,  in  different  plants  ?    B.  Sources  of  danger.    Determine  some 
of  these  by  actual  observations  on  (a)  birds  —  e.g.  note  the  food  of  flocks  of 
northern  birds  that  visit  your  locality  in  winter  —  and  (b)  other  animals. 
As  to  temperature,  it  may  be  asked,  Do  buds  freeze?    Does  freezing  kill? 
Does  prolonged  freezing  kill?    Does  thawing  kill?    C.   Methods  of  offsetting 
the  dangers  by  (a)  special  scales  (what  is  the  nature,  or  morphology,  of  the 
scales?),  (b)  coatings  of  the  parts  (wool,  glandular  secretions),  (c)  seclusion 
(1)  under  bark,  (2)  in  hollows,  (d)  other  means. 

III.  Experimental.    Earliest  date  at  which  buds  of  different  species  can  be 
made  to  open,  within  doors.    Effects  of  removing  some  or  all  of  the  scales  in 
certain  species.    Do  buds  grow  at  all,  in  diameter  or  length,  between  Decem- 
ber 1  and  March  1,  or  otherwise  change? 


V.    LABORATORY  STUDIES  OP  THE  ROOT 
EXERCISE  XIV.     THE  GENERAL  MORPHOLOGY  OF  THE  ROOT 

The  root  suggested  is  that  of  Shepherd's  Purse.  (Do  not  remove 
the  leaves  from  the  plants.) 

Note  the  general  habit  of  the  root  system,  consisting  of  one  main 
root  (taproot),  and  numerous  lateral  roots  and  rootlets. 

What  is  the  direction  of  growth  of  the 'taproot?  Of  the  lateral 
roots  ?  Examine  the  taproot  with  the  lens  for  contraction  wrinkles. 
Of  what  service  is  contraction  of  the  roots,  in  the  case  of  such  a  plant? 

Place  some  of  the  fine,  fibrous  rootlets  on  the  stage  of  the  dissecting 
microscope  in  water,  and  carefully  pick  apart  with  needles,  so  as  to  see 
their  length,  branching,  and  relative  slenderness.  Can  root  hairs  be 
made  out?  Does  the  branching  show  regularity?  Is  the  root  jointed 
where  branches  spring  out?  At  what  angle  do  the  branches  spring? 

Chip  away  one  side  of  the  main  root  to  show  the  wood  at  the  center. 
(In  doing  this,  save  half  or  more  of  the  upper  part  uncut,  for  later 
use.)  This  is  the  central  cylinder.  All  outside  of  this  is  the  cortex 
(bark).  By  scraping  and  stripping,  a  distinct  external  layer,  like  a 
skin,  may  be  detached  from  the  taproot.  This  resembles  the  external 


LABORATORY  STUDIES   OF  THE  ROOT  35 

layer  of  the  leaf  and  stem  in  being  more  or  less  impermeable  by  water. 
Does  the.  central  cylinder  of  the  taproot  connect  directly  with  those 
of  the  lateral  roots  and  rootlets? 

Experiment  7.  —  What  part  of  the  root  conveys  liquids  up  to  the 
leaves  of  the  shoot?  Determine  this  by  cutting  off  the  lower  half  of 
the  main  root  and  the  ends  of  some  other  roots,  and  placing  the  still 
leafy  plant  with  these  cut  surfaces  in  water  colored  with  eosin.  After 
a  tinu  cut  oft'  the  cortex  on  one  side  of  the  root,  at  different  levels,  to 
find  whether  the  eosin  water  has  been  taken  up ;  and,  if  so,  what  path 
it  has  followed.  Save  a  thin  cross  section  of  the  taproot  for  drawing. 
Draw  :  (1)  The  general  habit  of  the  root  system,  to  show  the  points 
already  mentioned.  Show  the  rings  or  wrinkles  due  to  longitudinal 
contraction.  (2)  A  piece  of  the  branching  fibrous  root  (as  seen  with 
the  dissecting  microscope,  and  therefore  much  magnified),  showing  the 
points  noted  above.  (3)  Longitudinal  section  of  taproot  (short  piece), 
showing  the  wood,  cortex,  and  coating,  and  the  connections  with 
branches  (  x  3-4).  (4)  Cross  section  of  the  taproot  (x  4-5). 

EXERCISE  XV.     ROOTS  FOR  CLIMBING 

Make  a  drawing  of  the  given  stem  with  its  climbing  roots,  to  show 
the  mode  of  occurrence  of  the  roots,  whether  in  rows  or  not,  and 
whether  at  or  near  the  nodes  of  the  stem  or  not.  With  the  lens, 
examine  the  roots  for  root  hairs.  Ts  there  any  sign  that  they  play  a 
part  in  the  adhesion  of  the  roots  to  supporting  surfaces? 

EXERCISE  XVI.     ROOTS  FOR  STORAGE 

Compare  the  internal  structure  of  the  given  root  with  that  of  Shep- 
herd's Purse.  Are  all  the  regions  which  were  observed  in  that  root 
found  in  this  one?  In  what  region  or  regions  of  the  storage  root  is 
thickening  most  pronounced?  In  what  part  or  parts  is  nourishment 
stored  ?  How  can  you  test  this  ?  What  part  does  this  root  play  in  the 
life  history  of  the  plant?  Will  the  root  grow  —  i.e.  give  rise  to  shoots 
—  when  planted  in  a  pot  of  earth  ?  (Try  it.) 

Is  any  part  of  the  stem  of  the  plant  present  and  closely  incorporated 
with  the  root?  Distinguish  root  and  stem  carefully  in  such  a  case. 

Draw  whatever  diagrams  are  necessary  to  illustrate  your  notes. 

Supplementary  Subjects 

1.  The  roots  of  epiphytic  Orchids.    Note  their  origin  and  structure,  and 
behavior  toward  water.     What  is  the  hahitat  of  these  plants  ? 

2.  Roots  of  the  Dodder. 

3.  Contraction  of  the  roots  of  plants. 

4.  Direction  of  growth  of  roots  under  influence  of  moisture. 

5.  The  rate  of  growth  of  the  roots  of  seedlings. 

6.  Koot  pressure  shown  hy  guttation. 


THE  ROOT 


VI.    THE  ROOT 

45.    Origin.  —  Roots  ordinarily  come  from  stems,  not,  as 
is  generally  thought,  stems  from  roots.     It  is  true  that  in 

springtime  flowering  herbs 
like  the  Trillium,  and  the 
Bloodroot  (Fig.  25),  are 
seen  to  break  from  the 
ground  as  if  produced  from 
a  root;  but  the  subter- 
ranean stock  in  all  such 
cases  is  a  true  stem. 

46.  Exceptions    to    the 
general  rule  are  not  uncom- 
mon, for  many  roots,  espe- 
cially if  severed  from   the 
stem,    have     a     power    of 
forming  afresh  within  their 
tissues,     buds     developing 
into  leafy  shoots.1 

47.  The  initial  stem  of 
the  embryo  produces  from 
its   end   a   root  which  be- 
comes the  first  or  primary 
root  of   the  plant.      Some 
plants  keep  this  as  a  main 

or  taproot  throughout  the  whole  of  their  life,  and  send  out 
only  small  side  roots  (Fig.  42);  but  commonly  the  main 
root  divides  off  very  soon,  and  is  lost  in  its  branches.  A 
root  system  is  thus  formed  with  no  marked  central  axis. 
In  plants  of  large  size,  as  trees,  the  roots  often  extend  on 
all  sides,  not  far  below  the  surface,  sometimes  to  a  con- 
siderable distance  beyond  the  limits  of  the  aerial  parts.2 

1  The  reproduction  of  lacking  parts  (as  buds  by  roots,  roots  by  stems, 
and  both  roots  and  stems  by  cut  leaves)  is  termed  regeneration.     The 
faculty  is  common  to  many  plants,  and  to  not  a  few  animals,  especially 
those  of  the  lower  types. 

2  "Those  of  an  elm  have  been  known  to  fill  up  drains  fifty  yards  dis- 
tant from  the  tree."  —  Goodale,  "  Physiological  Botany,"  p.  235. 


25.  The  Bloodroot,  producing  in  spring 
leaves  and  flowers  from  an  un- 
derground stem  which  is  popu- 
larly mistaken  for  a  root. 


THE  ROOT 


37 


48.  Every  flowering  plant,  with  some  rare  exceptions, 
has  thus  at  the  beginning  one  or  more  primary  roots  de- 
veloped from  the  tip  of  the  caulicle;  but 

when  occasion  arises,  additional  roots  are 
freely  produced  from  other  parts  of  the 
stem.  The  Poison  Ivy  is  a  woody  vine, 
sometimes  assuming  a  partially  erect, 
shrublike  habit.  Wherever,  in  clambering 
over  the  rocks,  the  stem  finds  shade  and 
moisture,  it  produces  a  thick  growth  of 
fibrous,  clinging  rootlets  (Fig.  26).  The 
higher  shoots,  rising  well  above  the  under 
shrubbery,  and  thus  exposed  to  sun  and 
air,  are  quite  devoid  of  them.  In  this  case 
the  accessory  roots  owe  their  existence  to 
causes  which  are  in  a  sense  accidental,  and 
they  are  accordingly  said  to  be  adventi- 
tious. 

49.  Any  part  of  the  stem  may  give  rise 
to  adventitious  roots,  but  they  come  most 
readily   from   the   nodes,   as  may  be   seen 
upon  examining  almost  any  creeping  plant 
(see  Figs.  34,  45). 


THE  FUNCTIONS   OF   ROOTS 

26.   Adventitious 
-/*      T>  P      i  j  •  roots  of  the 

50.  Roots  serve  as  organs  of  absorption  Poison  ivy. 
and  storage,  and  as  holdfasts. 

51.  Absorption.  —  They  absorb  water  and  dissolved  min- 
eral matters,  and  in  some  cases  organic  matter  left  by  the 
decay  of  former  vegetation,  or  even  the  juices  of  living 
plants. 

52.  Water  and  salts.  —  If  we  uncover  the  roots  of  a  tree, 
we  find  that  they  have  a  bark  impermeable  by  water.     This 
impermeable  covering  is  thicker  or  thinner  according  as  it 
is  older  or  younger,  but  is  never  altogether  lacking  until 
we  reach  the  young  rootlets.     Even  here  the  surface  is 
coated  with  a  substance  that  hinders  the  free  entrance  of 


88  THE  ROOT 

water,  except  for  a  short  distance  from  the  tip  backward. 
Only  the  parts  most  recently  formed  are  active  in  absorption. 

53.  The  production  of  new  rootlets  is  thus  of  high   importance. 
Accordingly,  as  long  as  the  plant  grows  above  ground,  and  expands 
fresh  foliage  from  which  moisture  largely  escapes  into  the  air,  so  long 
it  continues  to  extend  and  multiply  its  roots  in  the  soil  beneath,  re- 
newing and  increasing  the  fresh  surface  for  absorbing  moisture  in 
proportion  to  the  demand  from  above ;  and  when  growth  ceases  above 
ground,  and  the  leaves  die  and  fall  or  no  longer  act,  then  the  roots 
generally  stop  growing,  and  their  soft  and  tender  tips  harden.     From 
this  period,  therefore,  until  growth  begins  anew  the  next  spring,' is  the 
best  time  for  transplanting,  especially  for  trees  and  shrubs. 

54.  The   action  of   root   hairs.  —  It   has   already   been 
noted  in  the  laboratory  that  the  tip  of  the  seedling  root  is 
for  a  space  smooth,  but  that  at  a  little  distance  back  a 
thick  covering  of  root  hairs  soon  arises.     These  not  only 
insinuate  themselves  into  the  interspaces  of  the  soil  along- 
side of  the  root,  and  suck  up  whatever  water  may   be 

there  ;  but  they  apply 
themselves  closely  to  the 
soil  particles,  the  walls 
even  becoming  lobed  and 
distorted  in  order  to  gain 
closer  contact  with  the 

27.   A  root  hair,  much  magnified.    It  is  .   , 

seen  to  be  a  tubular  outgrowth     uneven  particles  compos- 

from  an  exterior  cell  of  the  root,      jnp.     ^he    Soil    (Tiff.     27). 
in  this  case  much  distorted.  ^        11 

tor  adhering  to  the  sur- 
faces of  the  latter  are  certain  substances  much  needed  by 
the  plant.  These  substances,  mineral  salts,1  are  not  re- 
moved by  the  simple  flow  of  soil  water,2  but  remain  firmly 
bound  until  acted  upon  by  the  root  hairs.  At  the  points  of 
contact,  the  root  hairs  excrete  an  acid  which  acts  to  release 

1  Salts  such  as  potassium  nitrate  (saltpeter),  magnesium   sulphate, 
calcium  phosphate,  etc. 

2  Fertilizers  applied  to  land  and  dissolved  by  the  rain  are  held  in  the 
same  manner  by  the  soil,  until  taken  by  the  roots  of  the  crops.    But  if 
applied  when  the  ground  is  frozen,  the  fertilizers  do  not  penetrate  the 
absorbent  soil  to  the  same  extent,  and  much  is  washed  away  by  surface 
drainage,  and  lost. 


THE  ROOT  39 

the  mineral  matters  in  question.  These  then  pass  into  the 
root  in  solution,  and  are  conveyed  to  the  parts  of  the 
plant  where  their  presence  is  required. 

55.  As  the  food  sought  becomes  exhausted  the  root 
hairs  cease  to  act,  and  after  a  short  time  die  and  fall  away. 
Meanwhile  further  on  new  hairs  have  been  put  forth  in 
soil  lately  invaded.     These  likewise  serve  their  turn  and 
shrivel.     In  this  manner  the  root  tip  in  its  progress  is 
followed  by  a  belt  of  absorptive  organs  which  explore  the 
soil  on  every  side  of  the  line  of-  advance. 

56.  Root  hairs  are  the  chief  organs  for  the  absorption  of 
water  and   dissolved   mineral  salts,  in  the    usual   cases. 
They  are,  however,  wanting  in  many  aquatics  and  even  in 
some  terrestrial  plants. 

57.  Protection  of  the  root 
tip.  —  In  growth  new  tissue 
is  formed  close  to  the  end  of 
the  root  (see  Fig.  28).     The 

very     forefront,      subject     to      28.   The  end  of  a  growing  root,  tipped 

wear  and  tear  by  the  resist-  and  protected  by  the  root  cap; 

*  g,  the  growing  point.     (Con- 

ance  Ot  the   SOll  to  the  root  S  siderably  magnified.) 

advance,  is  furnished  with  a 

shield  of  tissue,  somewhat  in  the  form  of  a  thimble,  which 
is  renewed  from  the  growing  point  within  as  fast  as  it  is 
worn  away  externally.  This  is  called  the  root  cap. 

58.  Aerial  roots  are  such  as  are  produced  above  ground. 
Some  of  the  most  highly  specialized  aerial  roots  are  those 
adapted  to  the  absorption  of  rain  and  dew.     Epiphytes  — 
that  is,  plants  seated  upon  other  plants,  but  not  living  at 
their  expense  —  are   obliged   to  depend  upon    occasional 
supplies  of  water,  which  the  roots  take  up  rapidly  at  the 
time  and  pass  on  to  the  leaves  and  stem  to  be  stored  for 
future  use.     Epiphytic  orchids  accomplish  this  by  means 
of  a  thick  spongy  layer  covering  nearly  the  entire  length  of 
their  numerous  aerial  roots  (Fig.  29). 

59-  Absorption  of  organic  food.. —  The  waste  from  decaying  vegeta- 
tion is  made  use  of  by  a  very  large  number  of  plants  having  no  other 
means  of  support.  These  are  saprophytes.  They  are  mainly  Crypto- 


40 


THE  ROOT 


gams  of  small  size,  but  among  them  are  several  flowering  plants.     The 
Indian  Pipe  is  common  in  woods,  where  its  short  stems  push  up  in 


29.  An  epiphytic  Orchid  with  numerous  aerial  roots  for  the 
absorption  of  rain  and  dew.  —  ScniMPEK.1 

little  groups  through  the  leaf  mold.  The  pale  hue  of  its  stem,  leaves, 
and  flower  remind  one  of  the  toadstools  in  company  with  which  it 
grows.  The  roots  are  adapted  to  absorb  organic  matters  in  solution 
from  vegetable  mold. 

60-  Parasitic  roots.  —  Part  of  the  roots  of  the  Yellow  Gerardia  are, 
or  may  be,  transformed  by  the  development  of  suckers  near  their 
tips,  by  which  they  grow  fast  to  the  roots  of  other  plants  and  steal 

nourishment  (Fig.  30).     At  the  same  time  the  Gerardia,  possessing 

• 

1  A.  F.  W.  Schimper,  "  Pflanzen-Geographie,"  1898.  An  account  of 
plants  ID  the  world -wMe  aspects  of  distribution  and  adaptation. 


THE  ROOT 


41 


green  coloring  matter,  is  able  like  all  green  plants  to  provide  for  itself; 
and  it  does  carry  on  the  work  of  forming  plant  food  in  a  quite  normal 


30.  Roots  of  the  Yellow  Gerardia,  some  of 
them  parasitic  on  the  root  of  a  Blue- 
berry bush. 


way  even  while  taking  the  sap 
of  other  plants.  This  is,  there- 
fore, the  case  of  a  partial  para- 
site. 

61.  Parasites  proper,  which 
strike  their  roots  into  the  tissues 
of  living  plants,  or  form  attach- 
ments to  their  surface  so  as  to 
suck  up  their  juices,  are  amongst 
the  most  interesting  of  all  vege- 
table forms.  Of  this  sort  is  the 
Mistletoe  (Fig.  31),1  the  ^seed 
of  which  germinates  on  the 
bough  where  it  falls  or  is  left 
by  birds ;  and  the  forming  root 
penetrates  the  bark  and  en- 
grafts itself  into  the  wood,  to 
which  it  becomes  united  as 
firmly  as  a  natural  branch  to 
its  parent  stem ;  and  indeed  the 
parasite  lives  just  as  if  it  were 
a  branch  of  the  tree  it  grows 

and  feeds  on.  A  most  common  parasitic  herb  is  the  Dodder  (Fig.  32), 
which  abounds  in  low  grounds  in  summer,  and  coils  its  long  and 
slender,  leafless,  yellowish  stems  —  resembling  tangled  threads  of  yarn 
—  round  and  round  the  stocks  of  other  plants;  wherever  they  touch, 
piercing  the  bark  with  minute  and  very  short  rootlets  in  the  form 
of  suckers,  which  draw  out  the  nourishing  juices  of  the  plants 
laid  hold  of.  Other  parasitic  plants,  like  the  Beech  Drops  and  Pine- 

1  Not  the  Mistletoe  proper  of  the  Old  World.  The  plant  represented  is 
an  American  relative  of  the  well-known  European  planjt,  very  much 
smaller,  and  properly  denominated  the  Dwarf  Mistletoe. 


31.   Plants  of  the  Dwarf  Mistletoe  para- 
sitic on  a  Branch  of  the  Spruce. 


42 


THE  ROOT 


sap,   fasten  their  roots  underground  upon  the  roots  of  neighboring 
plants,  and  rob  them  of  their  juices. 

62.     Roots  as  holdfasts. — This  function  comes    to   be 

of  great  importance  as 
the  plants  become  tall 
and  have  to  stand 
against  the  violence  of 
the  winds.  And  so 
the  main  roots  of  a 
tree,  spreading  abroad 
underground,  corre- 
spond in  girth  with 
the  largest  of  the 
branch  trunks  spread 
in  the  air  above. 
They  increase,  like  the 
trunk  and  limbs,  by 
the  annual  formation 
of  wood.  Yet  notwith- 
standing their  great 
size  and  strength, 
every  heavy  wind 
storm  leaves  here  and 
there  a  tree  over- 
turned. 

63.  Roots  for  climb- 
ing are  well  shown  by 
the  Trumpet  Creeper 
(Fig.  34).  Near  the 
nodes,  on  the  shaded 
and  moister  sides  of 
the  stem,  aeriaj.  roots 
are  produced  in  longi- 
tudinal rows,  and  become  matted  together  like  felt  by 
means  of  the  numerous  root  hairs  that  cover  them  through- 
out. As  the  young  stems  of  the  vine  push  upward  close 
to  the  face  of  a  wall  or  building,  these  webs  of  roots  grow 
out  until  tliey  strike  the  stone,  when  they  flatten  oiit  and 


32.  Dodder  parasitic  on  the  stem  of  an  herb. 
Note  the  absence  of  leaves  (except  a 
few  small  scales,  I) ,  the  development  of 
sucking  roots,  h,  and  the  flower  cluster. 
The  plant  has  no  connection  with  the 
ground,  except  in  the  seedling  stage. 


THE  ROOT 


h 


become  firmly  glued  to  the  surface.     Firm  support  is  thus 
p  afforded  to  the  ascending  creeper. 

64.  Roots  used  for  storage. —  The  roots 
of  almost  all  plants  that 
persist  for  more  than  a 
single  season  serve,  in 
common  with  the  stem, 
as  organs  of  storage,  to 
some  extent.  But  their 
forms  are  not  altered 
for  the  special  purpose 


oo.  A  section  through 
Dodder  and  host 
plant  at  the 
point  where  the 
haustorium,  or 
sucker,  of  the 
former  pene- 
trates the  bark 
of  the  host;  p, 
stem  of  the  para- 
site; s,  sucker, 
piercing  to  the  34.  Roots  of  Trum- 
woodof  the  host,  pet  Creeper, 

h  (much  magni-  used  in  clirnb- 

fied) .  —  SAC  HS.  ing. 


35.  Thickened  storage  roots  in 
cultivated  plants.  On  the 
left  Carrot,  on  the  right 
Radish.  In  both  cases  the 
root  is  confl  uent  above  with 
an  exceedingly  shortened 
stem  bearing  the  leaves. 


of  storage  in  ordinary  cases.  Yet  roots  are  sometimes 
much  enlarged  to  hold  the  nourishment  made  by  the 
plant  during  one  growing  season  for  its  use  in  the  next. 
Among  the  plants  that  owe  their  early  appearance  in  the 
spring  to  food  stored  up  in  a  somewhat  fleshy  root  is  the 
Dandelion  (Fig.  42).  In  certain  plants  the  tendency  to  a 
thickening  of  the  root  has  been  fostered  by  cultivation 
and  selection  until  from  the  original  wild  stock,  not  more 
promising  in  the  beginning  than  some  of  our  common 
herbs,  such  useful  food  plants  as  the  Beet,  Turnip,  Parsnip, 
and  Radish  have  been  produced.  These  make  use  of 


44 


THE  ROOT 


the  taproot  alone  (Fig.  35).     The  Anemonella  (Fig.  36), 
flowering   in    early   spring  with   the    more   familiar  and 

closely  related  Anemone, 
draws  upon  supplies  of 
food  held  in  a  cluster,  or 
fascicle,  of  roots.  A  fine 
example  of  adventitious 
roots,  some  of  which  remain 
fibrous  for  absorption,  while 
a  few  thicken  and  store  up 


37.  Roots  of  the  Sweet, 
Potato. 

food  for  the  next  season's 
growth,  is  furnished  by  the 
Sweet  Potato  (Fig.  37). 

DURATION  OF  ROOTS 

65.  Roots  are  said  to  be  an- 
imal,    biennial,     or      perennial. 
These  terms   apply  also  to   the 
whole  plant. 

66.  Annuals,  as  the  name  de- 

early    spring    growth    supplied      notes>   live    onlJ   for    one     year> 
from  a  fascicle  of  storage  roots,     generally  for  only  a  part  of  the 

year.     They  are  of  course  herbs ; 

they  spring  Irotn  the  seed,  blossom,  mature  their  fruit  and  seed, 
and  then  die,  root  and  all.  Annuals  of  our  temperate  climates  with 
severe  winters  start  from  the  seed  in  spring,  and  perish  at  or 
before  autumn.  Where  the  winter  is  a  moist  and  growing  season 
and  the  summer  is  dry,  winter  annuals  prevail;  their  seeds  germinate 


36.   Anemonella     thalictroides.      The 


LABORATORY  STUDIES   OF  THE  STEM  45 

under  autumn  or  winter  rains,  grow  mor?  or  less  during  winter,  blos- 
som, fructify,  and  perish  in  the  following  spring  or  summer.  Annuals 
are  fibrous  rooted. 

67.  Biennials,  of  which  the  Turnip,  Beet,  and  Carrot  are  familiar 
examples,  grow  the  first  season  without  blossoming,  usually  thicken 
their  roots,  laying  up  in  them  a  stock  of  nourishment,  are  quiescent 
during  the  winter,  but  shoot  vigorously,  blossom,  and  seed  the  next 
spring  or  summer,  mainly  at  the  expense  of  the  food  stored  up,  and 
then  die  completely. 

68.  Perennials  live  and   blossom  year  after  year.       A  perennial 
herb,  in  a  temperate  or  cooler  climate,   usually  dies  down   to   the 
ground  at  the  end  of  the  season's  growth.     But  subterranean  portions 
of    stern,   charged   with  buds,   survive    to  renew   the   development. 
Shrubs  and  trees  are  of  course  perennial;  even  the  stems  and  branches 
above  ground  live  on  and  grow  year  after  year. 


VII.  LABORATORY  STUDIES  OP  THE  STEM 

At  the  beginning  of  the  study  of  the  stem,  it  is  well  to 
recall  the  fact  that  a  flowering  plant  typically  consists  of 
root,  stem,  and  leaf.  Stems  and  leaves  may  be  so  dis- 
guised as  not  to  be  readily  recognized  in  their  true  charac- 
ter. Thus  some  stems  are  so  modified  as  very  closely  to 
resemble  leaves,  while  others  assume  the  general  appear- 
ance of  roots.  Yet  there  are,  with  few  exceptions,  certain 
marks  of  the  stem  proper  even  in  these  dissembled  forms. 

The  Marks  of  the  True  Stem 

1st.  The  stem  is  characterized  by  a  general  plan  of 
construction,  as  viewed  externally,  differing  essentially 
from  that  of  either  root  or  leaf. 

What  is  the  Plan  ? 

2d.    It  bears  appendages  at  certain  definite  places. 

What  are  the  Appendages? 

Where  inserted  upon  the  stem  ? 

3d.  If  the  stem  in  question  is  an  offshoot  from  an 
older  one,  its  point  of  origin  has  a  certain  definite  loca- 
tion. Position  determines  the  fact  that  a  lateral  member 
is  a  branch,  stem,  and  not  a  leaf. 


46  LABORATORY  STUDIES   OF  THE  STEM 

What  is  its  Position  ? 

These  are  the  questions  to  be  kept  in  mind  in  the  fol- 
lowing exercise. 

EXERCISE  XVII.     THE  CHARACTERISTIC  FEATURES  OF  STEMS 

Red  Maple.  —  Examine  with  care  all  marks  and  features  of  form 
and  the  position  of  the  branches  and  buds  with  respect  to  certain  of 
these  markings.  Examine  especially  the  newest  parts.  A  low  power 
of  the  hand  lens  brings  out  the  desired  points  well. 

Most  trees  and  shrubs  upon  the  approach  of  cold  weather  shield  the 
tender  extremities  of  their  stems  by  numerous  scales.  When  growth 
is  resumed  at  the  beginning  of  the  next  season,  the  scales  fall  away, 
leaving  scars  to  mark  the  occurrence  of  winter.  These  are  to  be  looked 
for  on  the  material  in  hand,  and  noted  as  interesting  traces  of  events 
in  the  recent  history  of  the  twigs.  But  such  annual  demarkations  are 
not  to  be  found  on  all  stems.  Refer  to  the  questions  immediately  pre- 
ceding this  exercise,  and  answer  them  in  the  notes.  The  sections  of 
the  stem  at  which  leaves  are  borne  are  called  nodes;  the  lengths 
between  leaves  are  internodes. 

Draw  the  terminal,  and  one  or  two  adjacent,  annual  lengths  of  the 
twig  —  enough  to  show  all  the  points  learned  in  the  study. 

EXERCISE  XVIII.     THE  INTERNAL  STRUCTURE  OF  STEMS1 

Looking  at  the  plants  of  the  fields  about  us,  we  perceive  the  great- 
est variety  in  the  size,  proportions,  and  attitude  of  stems.  In  some 
the  stem  is  so  short  as  to  seem  to  be  quite  wanting,  the  leaves  appear- 
ing to  spring  directly  from  the  root.  In  other  cases  the  stem,  elon- 
gated, reclines  upon  the  ground,  or  twines  for  support  upon  any  object 
within  reach. 

Yet  there  is  a  prevailing  type.  Its  erect  habit  and  height  most 
clearly  show  the  purpose  of  stems  in  general.  What  is  this  pur- 
pose ? 

As  height  from  the  ground  means  encounter  with  winds,  the  tall 
stem  must  also  be  strong.  Furthermore,  the  sap  has  a  considerable 
distance  to  travel  from  the  root  to  the  leafy  crown,  and  hence 
the  conduction  of  water  becomes  one  of  the  functions  of  the  stem. 

1  See  also  Chapter  XVII.  If  compound  microscopes  are  available,  the 
minute  structure  may  be  taken  up  more  in  detail  than  the  directions  here 
given  require.  In  any  case  use  should  here  be  made  of  figures  and  ex- 
planations from  Chapter  XVII.  The  cambium  region,  especially,  should 
be  located  even  under  the  dissecting  microscope,  and  its  meaning 
explained. 


LABORATORY  STUDIES   OF  THE  STEM  47 

These  considerations  lead  us  at  once  to  examine  the  internal  struc- 
ture. We  shall  expect  to  find  out  whether  the  internal  construction 
answers  to  the  uses  of  the  stem  or  not. 

1.   A  comparison  of  dicotyledonous  and  monocotyledonous  stems.  — 

Begonia  (dicotyledon^),  Asparagus  (monocotyledon). 

(1)  Even  a  naked-eye  examination  of  the  cross  sections,  held  up 
side  by  side  to  the  window  light,  shows  marked  differences.     Consider 
carefully  wherein  they  are  alike  and  wherein  dissimilar,  and  write  a 
comparative  account  of  the  cross  sections  as  you  see  them. 

(2)  Place  the  Begonia  section  under  the  highest  power  of  the  dis- 
secting microscope.     Notice  the  following  points  :  — 

(a)  The  central  space  is  filled  with  a  more  or  less  irregular  and 
indistinct  network,  in  which  some  meshes  (cells)  of  tolerably 
regular  form  may  be  made  out. 

(6)  Outside  of  this  is  an  interrupted  circle  of  somewhat  wedge- 
shaped,  denser  spots,  nearer  the  circumference  than  the  center 
of  the  section. 

(c)  Exterior  to  these  is  a  region  filled  by  a  network  of  large  cells. 
Toward  the  margin,  however,  the  cells  become  gradually 
smaller. 

The  outermost  layer  of  cells,  which  may  not  be  distinguishable,  is 
of  a  distinct  nature,  and  forms  the  epidermis. 

The  three  regions  thus  noted  are  characteristic  of  dicotyledonous 
stems.  They  are  (a)  pith,  (b)  hollow  cylinder  of  wood,  and  (c)  bark. 
Strictly  the  bark  includes  the  outer  ends  of  the  elongated  areas  noted 
under  (ft),  and  only  the  inner  half  or  two-thirds  is  wood.  (The  lens 
will  probably  show  the  division  line.)  In  this  fleshy  herbaceous  stem 
the  wood  does  not  form  a  complete  ring  in  the  cross  section,  it  will  be 
noticed.  The  Lilac,  soon  to  be  studied,  will  show  an  apparent  differ- 
ence in  this  respect. 

Draw  a  sector  of  the  cross  section,  showing  the  character  of  the 
three  regions  (x  5  —  10). 

(3)  Examine  in  the  same  manner  the  section  of  Asparagus. 
NOTE  :  —  (a)  The  large  cells  composing  by  far  the  greater  part  of 

the  section.     They  are  replaced  by  cells  of  a  different  char- 
acter in  two  instances ;  namely,  in 

(6)  The  scattered  darker  parts  which  much  resemble  the  denser 
areas  in  Begonia ;  and  in 

(c)  A  distinct  dense  ring,  not  far  from  the  edge  of  the  section. 

Finally  there  is 

(d)  The  outermost  zone,  composed  of  round  cells  of  uniform  size 

(the  epidermis). 

The  monocotyledonous  stem  has  no  separate  region  of  wood  includ- 
ing pith  and  surrounded  by  bark,  such  as  one  finds  in  dicotyledons. 
A  cylinder  of  firm  tissue  (c),  giving  a  degree  of  rigidity  to  the  stem, 


48  LABORATORY  STUDIES   OF  THE  STEM 

is  found  at  or  near  the  surface.  Throughout  the  loose  cellular  tissue 
(a)  the  wood  is  scattered  in  bundles,  or  strands  (6).  The  bundles 
are  tough  and  add  strength  to  the  stem,  and,  more  important  still,  fur- 
nish the  means  by  which  water  ascends.  The  sap  ducts  appear  in 
the  cross  section  as  large  circular  apertures  on  the  periphery  of  the 
bundles. 

Draw  a  sector  (60°)  of  the  monocotyledonous  stem  (  x  5-10). 

2.     The  woody  dicotyledonous  stem.  —  Lilac. 

(1)  The  first  cross  section  examined  should  be  of  the  end  twigs ; 
that  is,  of  the  stem  not  more  than  one  year  old. 

NOTE:  —  (a)  The  pith. 

(6)  The  wood,  which  seems  now  to  be  a  solid  ring.  A  high  power 
of  the  microscope,  however,  would  show  traces  of  pith  tissue 
running  out  to  the  bark  between  the  wood  wedges. 

(c)  The  bark,  beginning  at  the  outer  edge  of  the  wood.  Careful 
looking,  aided  by  lenses  of  even  moderate  power,  will  show  in 
the  inner  bark  region  a  ring  of  somewhat  glistening  bodies, 
distantly  resembling  a  string  of  beads.  These  are  the  ends  of 
bundles  of  bast  fibers.  What  is  a  possible  use  of  strong  fibers 
in  this  position  in  the  twig? 

Immediately  under  the  dark  outer  line  of  the  bark  are 
several  rows  of  cork  cells,  the  examination  of  which  may 
require  the  use  of  a  compound  microscope.  What  is  the  use, 
to  the  plant,  of  this  layer  of  cork  ? 

Draw  a  sector  of  the  cross  section  (90°),  to  show  these  parts. 

(2)  Make  smooth  cuts  across  the  twig  of  Lilac  where  it  is  one,  two, 
and  three  years  old  respectively.     Examine  the  ends  with  the  lens. 
In  what  part  of  the  stem  (what  part  of  the  cross  section)  is  new  wood 
annually  formed? 

Draw  the  three  cross  sections  in  diagram  (  x  3). 


EXERCISE  XIX.     THE  STRUCTURE  OF  WOOD  (OPTIONAL) 

First,  decide  which  side  of  the  block  furnished  for  examination  was 
toward  the  center  of  the  trunk.      Then  note  :  — 

(1)  The  annual  additions  of  wood. 

(2)  The  difference   in  appearance  between  spring  wood  and  fall 

wood.     What  makes  the  difference  (use  lens)  ? 

(3)  The  radiating  lines,  crossing  all  the  annual  layers  (rnea  illary 

rays). 

These  features  are  seen  on  the  cross-sectional  face.     Look  on  the 
other  faces  for  the  ends  of  the  medullary  rays  and  the  sap  ducts. 
Show  by  drawings  the  points  learned  from  the  study. 
Examine  also  a  piece  of  board  containing  a  knot.      Explain  the 


LABORATORY  STUDIES   OF  THE  STEM  49 

nature  and  origin  of  the  knot.     Are  trees  grown  in  the  open,  or  those 
grown  in  a  thick  forest,  more  likely  to  give  timber  free  from  knots? 


EXERCISE  XX.     THE  ASCENT  OF  SAP  IN  THE  STEM 

Experiment  8. — In  order  to  trace  the  course  followed  by  the  sap 
current  as  it  passes  from  the  root  to  the  leaves,  make  use  of  water 
tinged  with  eosin.  Put  the  cut  end  of  the  given  (leafy)  stem  in  the 
colored  water.  After  fifteen  or  twenty  minutes  examine  the  stem. 
If  it  is  translucent,  like  the  Balsam  (Impatiens),  the  course  of  the 
eosin  water  is  readily  seen  without  dissection.  Note  the  branching 
of  the  conducting  tissue  at  the  nodes. 

If  the  path  of  the  coloring  fluid  is  not  seen  from  without,  dissect. 

Having  determined  the  facts,  write  a  statement,  and  illustrate  by  a 
diagram  or  diagrams. 


EXERCISE  XXI.     GEOTROPISM  OF  THE  STEM 

The  manner  in  which  the  growing  plumule  behaves  toward  the 
attraction  of  gravitation  has  been  seen.  It  is  well  to  find  out  whether 
the  stem  retains  this  power  of  reaction  to  the  effect  of  gravity  at  a 
lator  date. 

Experiment  9.  —  This  may  be  done  by  turning  an  upright  potted 
plant  —  as  a  young  Sunflower  or  a  young  Nasturtium  —  into  a  hori- 
zontal position,  pot  and  all.  Make  a  diagram  of  pot,  stem,  and  one  or 
two  selected  leaves.  Leave  for  a  day.  Then  compare  with  the  diagram. 
Indicate  any  changes  by  making  dotted  lines  for  the  new  positions. 

Alternative.  Experiment  10.  —  The  leafy  scapes  of  the  Shepherd's 
Purse  (Capsella  Bursa-pastoris},  not  too  old,  make  excellent  subjects  for 
this  experiment.  Fit  the  scape  into  a  small  bottle  by  splitting  and 
grooving  the  cork.  Fill  the  bottle  quite  full  of  water  before  inserting 
the  scape  and  cork.  Fix  the  bottle  to  a  block  with  a  rubber  band,  to 
keep  the  bottle  from  rolling  when  the  arrangement  is  laid  on  its  side. 
After  making  a  diagram  of  the  stem,  etc.,  set  it  away  in  a  safe  place 
in  a  horizontal  position  until  the  next  day. 

Compare  with  the  diagram.  Represent  any  new  position  by  dotted 
lines  on  the  original  diagram. 

Write  full  notes. 

NOTE  :  —  The  same  scape  will  show  the  reaction  of  the  stem  to  light 
in  a  marked  manner,  at  least  if  taken  while  still  freely  growing. 
When  the  reaction  to  gravity  is  completely  apparent,  and  the  end  of 
the  scape  has  become  vertical,  place  the  scape,  still  in  its  bottle,  so  that 
it  faces  a  window.  In  front  and  shading  it  place  an  opaque  object  two 
or  three  inches  wide.  Draw  a  diagram  of  the  whole  arrangement,  and 

OUT.    OF    EOT. 4 


50  LABORATORY  STUDIES   OF  THE  STEM 

note  the  time.     Observe  the  scape  again  later,  looking  for  a  change 
from  the  original  attitude  of  the  stem. 

EXERCISE  XXII.     SPECIAL  USES  AND  FORMS  OF  STEMS 

Creeping  or  underground  stem.  —  Study  the  rhizome.  Look  for 
stem,  leaf,  and  root.  Which  are  present?  What  are  the  marks  show- 
ing the  true  nature  of  stem,  if  that  is  present?  What  is  the  distribu- 
tion of  the  roots,  if  present?  If  thickened,  does  the  rootstock  contain 
food  in  store  ? 

Draw  what  is  needed  to  illustrate  your  notes. 

Tuber  of  Potato.  —  First,  try  to  distinguish  between  the  tip  and  the 
base  of  the  tuber.  By  base  is  meant  the  end  by  which  the  Potato  was 
originally  attached  to  the  Potato  plant. 

Holding  the  tuber  right  end  up,  examine  it.  With  the  lens  look 
at  several  minute  prominences  within  the  depression  of  each  eye. 
These  are  buds. 

Below  is  a  ridge,  and  frequently  at  its  middle  point  may  be  seen 
a  small,  erect  scale.  What  is  the  morphology  of  this  scale  (subtend- 
ing a  bud)  ?  Test  the  pulp  Avith  iodine.  Morphologically,  what  is 
the  tuber?  AVhat  is  the  proof?  What  is  its  purpose  in  the  life  history 
of  the  potato  plant  ? 

Draw  an  enlarged  view  of  the  eye,  showing  ridge,  scale,  and 
rudimentary  buds  (  x  3-4). 

Houseleek.  —  (Optional.)  Examine :  (1)  The  green  heads,  with 
close-set,  thickish  leaves. 

(2)  The  dull-colored,  rootlike  parts  connecting  them.  Precisely 
whence  do  the  latter  spring?  In  what  do  they  end,  and  how?  Cut 
away  leaves  enough  to  determine  these  questions  clearly.  Have  they 
any  scars,  scales,  or  appendages  ?  What  is  their  morphology  ?  Proof  ? 
Cut  a  longitudinal  section  of  one  of  the  heads.  Note  the  sudden 
enlargement  of  the  axis  at  the  point  where  the  leaves  begin  to  be 
crowded.  Apply  dilute  iodine. 

Compare  the  stem  of  Houseleek  with  the  tuber  of  Potato  in  all 
respects,  —  as  to  organs  present,  the  comparative  development  of  these 
organs,  the  purpose  of  the  whole,  and  any  other  points. 

Draw  the  longitudinal  section  of  the  head. 

Asparagus.  —  Select  a  sprig  which  branches  several  times.  At  the 
base  of  every  branch  at  least  one  small,  scalelike  structure  is  found. 
What  is  it?  Follow  up  the  successive  subdivisions  of  one  of  the 
branches,  arriving  finally  at  the  smallest  members  of  the  ramification. 
At  each  dividing  note  a  similar  scale.  Is  it  found  at  the  foot  of  the 
needlelike  "leaves"?  If  so,  what  is  their  morphology?  Note  the 
color  of  all  parts  of  the  plant.  What  is  the  function  of  stem  in 
Asparagus  ? 


THF  STEM  51 

Draw  enough  of  the  stem  or  stems  to  show  the  points  discovered 
(x3). 

Crocus.  —  Remove  the  scales.  What  is  the  morphology  of  the 
denuded  bulb? 

Draw  the  stem,  showing  nodes,  internodes,  buds,  stolons  (under- 
ground, propagative  branches),  if  present. 

Cut  a  cross  section.  Is  the  plant  monocotyledonous  or  dicoty- 
ledonous? Test  for  starch.  What  is  the  life  history  of  this  plant? 

Flowering  Quince  (Cydonia  Japonica). 

Draw  a  thorn,  bearing  a  lateral  bud,  with  accessory  buds  at  the 
base,  and  the  subtending  leaf  scar  (  x  3}. 

Boston  Ivy  (Ampelopsis  Veitchii).  —  Are  the  tendrils  associated  in 
any  way  with  leaves  or  leaf  scars?  Answer  in  drawing  (x3).  Ex- 
amine the  tendril  itself  with  the  lens.  Are  there  any  indications  of 
leaf  formations  at  the  bases  of  the  branches?  Answer  in  drawing 
(x5).  What  is  the  use  of  the  flattened  ends  of  the  branches?  In- 
clude these  disks  in  one  of  the  drawings. 


VIII.     THE  STEM 

69.  The  stem  is  the  axis  of  the  plant  and  the  stock  from 
which   spring   all    the    other    organs.       Side    stems,    or 
branches,  spring  from  just  above  the  axils  of  the  leaves. 
Leaves  are  present  on  the  stem  of  every  flowering  plant  at 
some  stage  of  its  existence,  though  they  may    often  be 
reduced  to  the  merest  rudiments.     This  is  the  case  with 
stems  that  run  along  beneath  the  surface  of  the  soil,  where 
leaves  would  be  of  no  use.     But  the  tendency  to  produce 
leaves  never  quite  disappears,  and  on  underground  steins 
manifests  itself  in  scales  and  prominences  at  more  or  less 
uniform  distances  ;  the  joints  or  nodes  thus  made,  serving 
to  distinguish  such  stems  from  roots,  which  they  otherwise 
closely  imitate. 

70.  The  stem  of  an  annual  herbaceous  plant  is  composed 
largely  of  living  tissue,  and  is  commonly  seen  to  be  green, 
pulpy,  more  or  less  translucent,  and  full  of  sap.     A  few 
strands  of  woody  fiber  run  through  it  ;   but  the  general 
mass  is  succulent,  and  abounds  in  living  substance.     As 
age   and  height  and  the  weight  of  foliage  and  fruit  in- 
crease, woody  strengthening  tissue  may  be  largely  devel- 


52  THE  STEM 

oped  even  in  annual  stems.  If  the  plant  is  a  perennial, 
especially  if  it  grows  to  a  considerable  height,  the  wood 
increases  and  the  living  tissue  becomes  a  relatively  smaller 
part  of  the  whole.  In  the  stems  of  trees  the  living  por- 
tions comprise  only  the  growing  tips  of  branches,  the 
younger  bark,  and  a  film  of  active  tissue  just  outside  the 
wood.  The  bark  (except  those  parts  freshly  formed),  and 
the  cylinders  of  wood,  are  essentially  dead,  and  serve 
merely  mechanical  purposes  in  the  support  and  protection 
of  that  which  is  alive. 

71.  The  growth  of  stems.  — Stems  increase  in  length  at 
or   near  the   young  tips.     In    plants   of   definite  annual 
growth  the  number  of  internodes —  or  interspaces  between 
leaves  —  is  predetermined  in  the  bud.     Early  in  the  fol- 
lowing season  these  internodes  gain  their  full  extension 
and  thereafter  remain  fixed  in  length.      Girth  increases 
through  the  formation  of  wood  by  the  living  tissue  that  sur- 
rounds the  woody  cylinder.     Growth  is,  of  course,  inter- 
rupted as  often  as  severe  cold  or  extreme  drought  sets  in  ; 
and  in  those  parts  of  the  world  where  this  is  a  regularly 
recurring  event,  the  wood  is  formed  in  successive  layers. 
When  cut  across,  the  layers  appear  as  rings.     Stems  of  trees 
and  shrubs  grown  in  temperate  climates  show  in  the  cross 
section  the  spring  wood  —  laid  down  when  growth  is  par- 
ticularly active  —  differing  in  color  or  texture  from  the 
fall  wood.     The  age  of  trees,  therefore,  is  easily  made  out 
when    the   trunk   is   cut   off.     Sometimes,  however,  two 
rings   are   formed  in  a  single    season,  when    midsummer 
drought  interrupts  the  regular  growth.     Allowance  must 
be  made  for  these  cases  in  estimating  the  age  of  trees. 

72.  The  direction  of  growth.  —  Most  stems  grow  upward; 
that  is,  toward  the  light ;   for  it  is  the  benefit  got  by  full 
exposure  of  the  foliage  to  the    sun  that  has  led  to   tall 
stems.     Leaves  of  tall-stemmed  plants  are  raised  out  of 
the  shade  cast  by  crowding  neighbors. 

73.  Upright  stems  include,  besides  the  ordinary  rigid 
and  self-sustaining  type,  many  climbing  forms.     Certain 
ones  gain  the  advantages  of  elevation  by  twining  upon  the 


THE  STEM  53 

stems  of  other  plants  for  support  (Fig.  38),  and  often 
grow  until  they  spread  their  own  leaves  above  those  of  the 
plants  that  they  encum- 
ber. The  way  in  which 
such  climbers  bend  from 
side  to  side  until  they 
strike  some  vertical  sup- 
port may  be  told  in  the 
words  of  Darwin  :  -  t^jj^)}  n  38-  Twining  stem  of  the 

Morning  Glory. 
"  When  the  shoot  of  a  hop 
rises  from  the  ground,  the  two 
or  three  first-formed  joints  or 
internodes  are  straight  and 
remain  stationary ;  but  the  next-formed,  whilst  very  young,  may  be 
seen  to  bend  to  one  side  and  to  travel  slowly  around  towards  all 
points  of  the  compass,  moving  like  the  hands  of  a  clock,  with  the  sun. 
The  movement  very  soon  acquires  its  full  ordinary  velocity.  From 
seven  observations  made  during  August,  and  on  another  plant  during 
April,  the  average  rate  during  hot  weather  and  during  the  day  is  two 
hours  eight  minutes  for  each  revolution  ;  and  none  of  the  revolutions 
varied  much  from  this  rate.  The  revolving  movement  continues  as 
long  as  the  plant  continues  to  grow;  but  each  separate  internode, 
as  it  becomes  old,  ceases  to  move." 

74.  The  revolutions  are  less  rapid  at  night  than  in  the 
daytime,  but  are  maintained  until  some  object  of  support 
is  met  with,  when  the  free  extremity  still  goes  on  revolv- 
ing  and    the   stem    shortly   encircles  the  support.     The 
movement  then  continues  in  an   upward-winding  spiral, 
the  coils  tightening  and  the  twiner  steadily  ascending. 

75.  Most  species  of  twining  plants  wind  in  a  definite 
direction.     That  is,  as  we  look  down  upon  the  plant,  the 
revolving  tip  moves  with  the  hands  of  a  watch  lying  face 
upward,  in  some  species ;  opposite  to  the  hands,  in  other 
species. 

76.  Another  class  of  climbing  plants  includes  those  that 
simply  clamber  in  a  haphazard  fashion  through  and  over 
the  surrounding  herbage.     The  thorns  of  many  Brambles 
and  the  minute  backward-pointing   hooks   studding  the 
angles  of   the  stems  and  the  margins  of   the  leaves  in 


54 


THE  STEM 


The  stem  and  leaves  of  Galiiim,  or 
Bedstraw,  studded  with  backward 
pointing  hooks  (magnified). 


Galium  (Fig.  39),  catching  on  leaves  and  branches,  pre- 
vent these  climbers    from  slipping  from   their  supports. 

If  we  attempt  to  pull 
a  tangle  of  Galium  away 
from  the  foliage  of  the 
herbs  and  shrubs  over 
which  it  runs,  the  plant 
itself  is  torn  in  pieces 
before  we  succeed  in 
dislodging  it. 

77.  Of  special  organs 
for  climbing,  the  clinging 
rootlets  of  the  Trumpet 
Creeper  have  already 
been  described.  Leaves,  and  parts  of  leaves  serving  the 
same  general  purpose,  but  adapted  in  a  much  more 
remarkable  manner  to  a  climbing  habit,  will  be  described 
in  the  next  chapter.  In  the  list  of  specialized  climbing 
organs  there  still  remain  certain  stems,  modified  into 
either  adherent  or  twining  tendrils. 

78.  Adhesive  disks.  —  The  Virginia  Creeper  illustrates 
the  first  case.     The  tips  of  certain  branches  are  flattened 
into    disks   with    an 

adhesive  face  (Fig. 
40).  This  is  applied 
to  the  supporting 
object,  to  which  it  be- 
comes firmly  glued. 
Then  a  shortening 
of  the  branches  by 
coiling  brings  up  the 
growing  shoot  close 
to  the  support.  This  is  an  adaptation  to  climbing  mural 
rocks  and  walls  or  the  trunks  of  trees,  to  which  the 
vine  would  not  be  able  to  cling  by  means  of  twining 
tendrils. 

79.  Twining  tendrils.  —  Some  tendrils  are  leaves  or  parts 
of  leaves,  as  those  of  Cobcea  (Fig.  73).     The  nature  of  a 


40.  Tendrils  of  Virginia  Creeper. 


THE  STEM 


55 


41.  Tendrils  of  the  Pas 
sioii  Flower. 


tendril  is  known  by  its  position.     A  tendril  from  the  axil 
of  a  leaf,  like  that  of  the  Passion  Flower  (Fig.  41),  is,  of 
course,  a  stem,  i.e.  a 
branch. 

80.  In   the  young 
stage,  when  still  ex- 
tended,   tendrils   are 
endowed  with  motion 
and    with    sensitive- 
ness     to     contact. 
Their  movements  are 
like  those  of  twining 
stems,  —  they       de- 
scribe   circles   or   el- 
lipses  until    brought 
against  some  object. 

When,  by  the  curving  of  the  tip,  a  hold  has  been  secured 
upon  this  object,  the  tendril  coils  in  a  double  spiral. 
The  coil  or  spiral  itself  is  of  importance  in  all  such 
cases,  for  its  elasticity  prevents  a  sudden  stress  caused, 
for  example,  by  a  blast  of  wind,  from  snapping  the 
tendril  off,  as  might  be  the  result  were  the  tendril 
straight  and  already  tightly  drawn  at  the  moment  of 
onslaught. 

"  I  have  more  than  once  gone  on  purpose,  during  a  gale,  to  watch  a 
Bryony  growing  in  an  exposed  hedge,  with  its  tendrils  attached  to  the 
surrounding  bushes;  and  as  the  thick  and  thin  branches  were  tossed 
to  and  fro  by  the  wind,  the  tendrils,  had  they  not  been  excessively 
elastic,  would  instantly  have  been  torn  off  and  the  plant  thrown  .pros- 
trate. But  as  it  was,  the  Bryony  safely  rode  out  the  gale,  like  a  ship 
with  two  anchors  down,  and  with  a  long  range  of  cable  ahead  to  serve 
as  a  spring  as  she  surges  to  the  storm."  —  DARWIN. 

81.  The  tendrils  of  the  Passion  Flower  are  wonderfully  sensitive  to 
slight  pressure.    In  Darwin's  experiments,  "  A  bit  of  platinum  wire,  ^ 
of  a  grain  in  weight,  gently  placed  on  the  concave  point,  caused  a 
tendril  to  become  hooked,  as  did  a  loop  of  soft,  thin  cotton  thread  ^ 
of  a  grain.     The  point  of  a  tendril  of  Passiflora  gracilis  began  to  move 
distinctly  in  twenty-five  seconds  after  a  touch,  and  in  many  cases  after 
thirty  seconds." 


56 


THE  STEM 


82.  So-called  stemless  plants.  —  At  the  opposite  end 
of  the  scale  from  the  plants  with  tall  stems,  rising  as  high 
as  possible  toward  the  sources  of  light,  are  those  that,  like 
the  Dandelion  (Fig.  42),  reduce  the  leaf-bearing  axis  to 
the  shortest  possible  span.  Owing  to  the  extreme  brevity 
of  the  stem,  and  perhaps  as  well  to  the  difficulty  of 


42.  Root,  shortened  stem,  buds,  and  leaves,  of  the  Dandelion. 

distinguishing  the  stem  portion  from  the  taproot,  these 
plants  are  sometimes  spoken  of  as  stemless.  A  better  term 
is  acaulescent  (which  literally  means  becoming  stemless). 
The  summit  of  the  stem — in  the  Dandelion  —  is  at  the 
level  of  the  ground,  or  slightly  lower.1  Crowded  together 
by  the  shortening  of  the  internodes,  the  leaves  radiate  in 

1  The  roots  of  some  plants,  after  gaining  a  firm  hold  on  the  earth,  con- 
tract and  gradually  draw  the  stem  into  the  soil. 


THE  STEM  57 

the  form  of  a  rosette,  and  pressing  back  the  grass  and 
other  low  herbage,  make  a  way  for  the  inflow  of  light. 
At  the  same  time  the  stem,  with  the  growing  point  and 
much  of  the  foliage,  is  safe  from  the  teeth  of  grazing 
animals :  though  it  would  be  hard  to  say  just  how  much 
this  kind  of  security  has  had  to  do  with  the  development 
of  the  shortened  stem.  For  other  advantages  of  the  acau- 
lescent  habit  may  have  played  a  part  in  the  gradual  acquire- 
ment of  a  shortened  stem  through  successive  generations 
of  Dandelionlike  plants ;  such  as  the  increased  moistness 
of  the  half-subterranean  situation,  and  the  relatively  stable 
temperature  of  the  soil. 

83.  Certain  stems  develop  wholly  beneath  the  surface,  as  we  shall 
presently  see,  the  leaves  alone,  with  the  flowering  axis,  appearing  above 
ground.     To  such  forms  as  these  the  Dandelion  and  other  acaulescent 
plants  offer  a  natural  transition  from  the  ordinary  aerial  type.     In  the 
buried  stems  the  habit  of  taking  refuge  in  the  soil  is  fully  formed.     In 
the  Dandelion  it  may  be  in  process  of  formation.     At  least  we  may 
see  in  the  latter  one  stage  in  the  change  of  habit  by  which  the  Jack- 
in-the-pulpit,  for  example  (Figs.  50,  173),  has  become,  as  to  its  stem, 
a  confirmed  dweller  beneath  ground. 

84.  Thus  far  only  vertical  stems,  or  stems  of  a  more  or 
less  upright  character,  have  been  considered.     There  are 
all  gradations  between  these  and  prostrate  or  horizontal 
forms,  many  species  habitually  taking  a  leaning  attitude, 
between  the  vertical  and  the  horizontal. 

85.  Of  the  creeping,  or  repent,  kinds  the  Partridge  Berry 
is  a  good  example.     It  frequents  moderately  shaded  situ- 
ations, especially  open  woods,  where  it  runs  along  upon 
the  ground,  striking  root  at  short  intervals  and  spreading 
its  small,  rounded,  evergreen  leaves  quite  close  to  the  sur- 
face.    Each  year  it  is  covered  by  the  leaves  fallen  from 
the  trees.     These  accumulate  from  season  to  season  upon 
the  older  parts  of  the  stem,  which  thus  finally  becomes 
partly    subterranean   through   burial   by   the   leaf   mold, 
loses  its  leaves,  and  gradually  decays  at  the  older  extrem- 
ity.    The  young,  growing  sections  of  the  shoot,  not  more 
than  a  year  or  two  old,  push  forward  continually,  over 
the  dead  leaves,  and  thus  remain  subaerial.     Such  cases 


58 


THE  STEM 


43.   Bulblets  of  the  Tiger  Lily. 


as  this  perhaps  represent  the  first  step  in  the  process  of 
change  by  which  the  ancestors  of  our  Bell  wort  (Fig.  20) 
and  Bloodroot  (Fig.  25)  became  subterranean  in  habit. 

86.  Stems  for  propagation;  that  is,  for  the  establish- 
ment of  new  individual  plants.  Many  plants  reproduce 
their  kind  without  the  intervention  of  seed.  Some  part 
of  the  original  plant  is  separated  from  the  parent  stock 
and  develops  into  a  new  plant.  This  is  termed  vegetative 
reproduction,  to  distinguish  it  from  reproduction  by  seed. 
The  Potato  is  regularly  propagated  by  this  method,  as 
also  in  the  tropics  are  Sugar  Cane,  the  Banana,  and  the 
Pineapple,  none  of  which  ordinarily  produce  seed. 

87.  A  curious  mode  of  vegetative 
reproduction  is  by  the  bulblets,  or  small 
bulbs,  formed  in  the  axils  of  the  leaves 
of  certain  garden  Lilies  (Fig.  43),  and 
often  in  the  flower  clusters  of  the  Onion. 
They  are  plainly  buds  with  thickened 
scales.  They  never  grow  into  branches, 

but  detach  themselves  when  full  grown,  fall  to  the  ground,  and  take 

root  there  to  form  new  plants. 

88.  A  stolon  is  a  branch  from  above  ground,  which  reclines  or 
becomes  prostrate  and  strikes  root  (usually  from  the  nodes)  wherever 
it  rests  on  the  soil.     Thence  it  may  send  up  a  vigorous  shoot,  which 
has  roots  of  its   own,  and  becomes  an 

independent  plant  when  the  connecting 
part  dies,  as  it  does  after  a  while. 

89.  An  offset  is   a   short  stolon,   or 
sucker,  with  a  crown  of  leaves  at  the  end, 
as  in   the    Houseleek  (Fig.  44),  which 
propagates  abundantly  in  this  way. 

90.  A  runner,  of  which   the   Straw- 
berry presents  the   most   familiar   and 
characteristic    example,   is   a  long   and 

slender,  tendril-like  stolon,  or  branch  from  next  the  ground,  destitute 
of  conspicuous  leaves.  Each  runner  of  the  Strawberry,  after  having 
grown  to  its  full  length,  strikes  root  from  the  tip  becoming  fixed 
to  the  ground,  then  forms  a  bud  there,  which  develops  into  a  tuft  of 
leaves,  and  so  gives  rise  to  a  new  plant,  which  sends  out  new  runners 
to  act  in  the  same  way.  In  this  manner  a  single  Strawberry  plant 
will  spread  over  a  large  space,  or  produce  a  great  number  of  plants, 
in  the  course  of  the  summer,  all  connected  at  first  by  the  slender 


44.  Houseleek,     propagating 
by  offsets. 


I  UK  STEM 


59 


runners;  but  these  die  in  the  following  winter,  if  not  before,  and 
leave  the  plants  as  so  many  separate  individuals. 

91.    Subterranean  stems  and  branches.  —  These  are  very 
numerous  and  various.     The  vegetation  that  is  carried  on 


46.   Rhizome  of  the  Iris. 


45.  Khizoines  of  the  Peppermint. 

underground  is  hardly  less  varied 
or  important  than  that  above 
ground.  All  their  forms  may  be 
referred  to  four  principal  kinds  : 
namely,  the  Rhizome,  or  Rootstock, 
the  Tuber,  the  Corm  or  solid  bulb, 
and  the  true  Bulb. 


92.  The  rootstock,  or  rhizome,  in  its 
amplest  form,  is  merely  a  creeping  stem 
or  branch  growing  beneath  the  surface  of  the  soil,  or  partly  covered 
by  it  (Fig.  45). 

93.  Rootstocks  are  commonly  thickened  by  the  storing  up  of  con- 
siderable nourishing  matter  in  their  tissue.     The  common  species  of 
Iris  (Fig.  46)  in  the  gardens  have  stout  rootstocks,  which  are  only 
partly  covered  by  the  soil,  and  which  bear  foli- 
age leaves  instead  of  mere  scales,  closely  covering 

the  upper  part,  while  the  lower  produces  roots. 

94.  A  tuber  may  be  understood  to  be  a  por- 
tion of  a  rootstock  thickened,  and  with  buds 
(eyes)  on  the  sides.     Of  course,  there  are  all 

gradations  between  a  tuber 

and    a  rootstock.      Helian- 

thus  tuberosus,  the  so-called 

Jerusalem  Artichoke  (Fig. 

48),      and      the      common 

Potato,  are  typical  and  fa- 
miliar ex- 

,          ,.       47.  Corm  or  Caudex. 
amples  of  of  Trillium. 

the  tuber. 

The  stalks  by  which  the  tubers 
48.  Tubers  oi  Heliantlms  tuberosus.       are  attached  to  the  parent  stem 


60 


THE  STEM 


are  at  once  seen  to  be  different  from  the  roots,  both  in  appearance 
and  manner  of  growth.  The  scales  on  the  tubers  are  the  rudiments 
of  leaves ;  the  eyes  are  the  buds  in  their  axils.  The  Potato  plant 
rears  annual  stems  that  bear  ordinary  leaves  expanded  in  the  air,  to 
digest  what  they  gather  from  it  and  what  the  roots  gather  from  the 
soil,  and  convert  these  substances  into  nourishment.  A  large  part  of 
this  nourishment,  while  in  a  liquid  state,  is  carried  down  the  stem,  into 
the  underground  branches,  and  accumulated  in  the  form  of  starch  at 
their  extremities,  which  become  tubers,  or  depositories  of  prepared  solid 
food,  — just  as  in  the  Turnip,  Carrot,  and  Anemonella  (Figs.  35,  36), 
it  is  deposited  in  the  root.  Taking  advantage  of  this,  man  has  trans- 
ported the  Potato  from  the  cool  Andes  of  Chile  to  other  cool  climates, 
and  made  it  yield  him  a  copious  supply  of  food,  especially  important 
in  countries  where  the  season  is  too  short,  or  the  summer's  heat  too 
little,  for  profitable  cultivation  of  the  principal  grain  plants. 


49.   Cyclamen. 


50.   Indian  Turnip  (Arissema). 


95.  The  corm  or  solid  bulb,  like  that  of  Cyclamen  (Fig.  49),  and 
of  Indian  Turnip  or  Jack-in-the-pulpit  (Fig.  50),  is  a  very  short  and 
thick  fleshy  subterranean  stem,  often  broader  than  high. 

96.  The  bulb,  strictly  so-called,  is  a  stem  like  a  reduced  corm  as  to 
its  solid  part  (or  plate) ;  while  the  main  body  consists  of  thickened 

scales,  which  are  leaves  or  leaf 
bases.  These  are  like  bud 
scales;  so  that  in  fact  a  bulb  is 
a  bud  with  fleshy  scales  on  an 
exceedingly  short  stem.  Com- 
pare a  White  Lily  bulb  (Fig.  51) 
with  the  strong  scaly  buds  of 
the  Hickory  (Fig.  17),  and  the 
resemblance  will  appear.  In 
corms,  as  in  tubers  and  root- 


51.  Bulb  of  White  Lily.  The  longitudi- 
nal section  shows  two  buds  of 
the  next  year. 


stocks,  the  store  of  food  for 
future  growth  is  deposited  in  the 
stem;  while  in  the  bulb,  the 
greater  part  is  deposited  in  the  bases  of  the  leaves,  changing  them 
into  thick  scales,  which  closely  overlap  or  inclose  one  another. 


THE  STEM 


61 


97.  A  scaly  bulb  (like  that  of  the  Lily,  Fig.  51),  is  one  in  which 
the  scales  are  thick  but  comparatively  narrow. 

98.  A  tunicated  or  coated  bulb  is  one  in  which  the  scales  enwrap 
each  other,  forming  concentric  coats  or  layers,  as  in  Hyacinth  and 
Onion. 

99.  Stems  as  foliage.  —  All  green  parts  of   the  plant, 
whether  belonging  to  the  leaf  or  to  the  stem,  serve  the 
same  purpose  as  the  foliage  to  some  extent ;  for  example, 
the  green  twigs  of  a  tree  and  the  green  stem  of  an  herb. 


52.  Flattened  leaflike  steins  of  Muhlenbeckia  ptoty- 
clados,  bearing  flower  clusters  at  the  nodes. 

A  considerable  number  of  plants  have  come  to  dispense 
with  leaves  entirely,  modified  stems  doing  their  work. 
Thus,  in  the  Asparagus  what  appear  to  be  needle-like 
leaves  are  in  reality  branches  springing  from  the  axils  of 
the  true  leaves;  the  leaves  themselves  being  minute,  dry 
scales.  In  Muhlenbeckia  (Fig.  52)  the  nodes  of  the  stem 


62  THE  STEM 

are  very  well  marked,  but  they  bear  only  small  temporary 
leaves  or  none  at  all.  The  stems  are  adapted  to  function 
as  leaves  by  being  flattened  and  by  retaining  the  green 
color  necessary  for  active  foliage.  Thus  many  desert 


53.  Opuntia  Jilipendula.  A  Prickly  Pear  Cactus,  and 
typical  desert  plant,  having  a  thickened  stem  with 
green  rind,  numerous  protective  spines  hut  no 
foliage  leaves.  The  roots  are  partly  transformed 
by  tuberous  swellings  into  organs  of  storage ;  when 
planted  they  grow,  like  the  thickened  roots  of  the 
Sweet  Potato. 

plants  like  the  Cactuses  (Fig.  53)  have  no  foliage  leaves. 
The  green  rind  takes  on  their  function.  The  total  sur- 
face of  these  plants  is  thus  very  small  compared  with 
the  surface  exposed  by  a  leafy  plant  of  the  same  bulk, 
growing  in  moist  climates.  The  water  that  the  desert 
plants  are  able  to  obtain  through  their  roots  in  the  wet 


THE  STEM  63 

season   is   therefore  not  lost,  or  lost  only  with  extreme 
slowness,  in  the  dry  period. 

100.  To  all  more  or  less  flattened  stems  thus  modified 
to  serve  as  foliage  (e.g.  Asparagus,  Muhlenbeckia,  Prickly 
Pear)  the  name  phyllocladia  (singular  phyllocladium)  has 
been  given. 

101.  The  longevity  of  trees.  —  The  duration  of  the  stem  is  the 
duration  of  the  plant,  for  the  stem  is  the  permanent  seat  of  life  in 
plants,  the  part  from  which  new  organs  arise  and  new  shoots  of  the 
same  individual  are  produced.     When  the  stem  dies,  the  plant  as  an 
individual   perishes.1     In  considering  stems,  therefore,  the  length  of 
life  of  plants  is  naturally  suggested.     Annual,  biennial,  arid  perennial 
are  terms  already  explained  in  the  chapter  on  the  root.     Many  of  the 
perennial  herbs,  such  as  the  acaulescent  kinds,  live  for  a  comparatively 
long  time,  without   forming  any  considerable  quantity  of  wood  or 
much  increasing  the  length  of  the  stem,  probably  for  a  dozen  or  a 
score   of  years.2     The   continuance   of  life   in   shrubs   and   trees   in 
these  cases  is  often  great  compared  with  that  of  human  life,  and  in 
not  a  few  cases,  is  exceedingly  great,  so  that  single  trees  still  living  are 
known  to  have  sprung  from  the  seed  long  before  any  but  the  oldest 
of  existing  nations  came  into  being.      "The  celebrated  Lime  of  Neu- 
stadt  in  Wiirtemberg  is  between  eight  hundred  and  one  thousand 
years  old ;  the  age  of  the  Fir  of  Beque  is  estimated  at  twelve  hundred 
years,  and  a  Yew  in  Braburn  (Kent)  is  at  least  as  old."3    John  Muir 
cites  two  cases  of  Sequoias,  the  Big  Trees  of  California,  determined 
by  the  annual  rings  as  being  respectively  thirteen  hundred  and  twenty- 
two  hundred  years  old ;  though  the  latter  was  "  not  a  very  old-looking 
tree."     "  Under  the  most  favorable  conditions  these  giants  probably 
live  five  thousand  years  or  more,  though  few  of  even  the  larger  trees 
are  more  than  half  as  old.     I  never  saw  a  Big  Tree  that  had  died  a 
natural  death  ;    barring  accidents  they  seem  to  be  immortal,  being 
exempt  from  all  the  diseases  that  afflict  and  kill  other  trees.     Unless 
destroyed  by  man,  they  live  on  indefinitely  until  burned,  smashed  by 
lightning,  or  cast  down  by  storms,  or  by  the  giving  way  of  the  ground 
on  which  they  stand.  .  .  .     The  colossal  scarred  monument  in   the 
King's  River  forest  mentioned    above  is  burned  half   through,   and 

1  Though,  as  has  been  stated,  the  roots  even  when  cut  away — or  when 
the  stern  is  removed  —  may  produce  new  buds.     But  these  are  out  of  the 
ordinary  course  of  events,  and  in  a  sense  result  in  new  individuals,  not 
the  continuance  of  the  old. 

2  The  only  available  data  seem  to  be  casual  observations.       The  sub- 
ject is  an  excellent  one  for  definite  observations  and  record. 

8  Strasburger,  "Text  Book  of  Botany,"  1898,  p.  239. 


64  THE  STEM 

I  spent  a  day  in  making  an  estimate  of  its  age,  clearing  away  the 
charred  surface  with  an  ax,  and  carefully  counting  the  annual  rings 
with  the  aid  of  a  pocket  lens.  The  wood  rings  in  the  section  I  laid 
bare  were  so  involved  and  contorted  in  some  places  that  I  was  not  able 
to  determine  its  age  exactly,  but  I  counted  over  four  thousand  rings, 
which  showed  that  this  tree  was  in  its  prime,  swaying  in  the  Sierra 
winds  when  Christ  \valked  the  earth."1 

102-  Types  of  adaptation.  —  Plants  are  machines  fitted  to  do  work 
under  certain  conditions.  The  work  done  by  the  plant  is  to  take  cer- 
tain materials  into  itself,  move  them  about,  break  them  up  chemically, 
recombine  them  into  new  compounds,  and  build  up  its  body,  adding 
to  old  parts  and  organizing  new  parts.  Certain  new  parts  finally 
become  new  individuals.  Growth  and  reproduction,  and  the  moving 
of  materials  for  these  purposes,  are  the  work  of  the  plant  machine. 

The  conditions  under  which  the  work  is  done  are  dependent  upon 
the  nature  of  surrounding  materials  and  the  nature  of  certain  forces 
affecting  the  plant.  Of  materials,  there  are  soil,  water,  and  air ;  of 
forces,  chiefly  heat  and  light.  Each  of  these  conditioning  factors 
varies  from  place  to  place.  The  composition  of  the  soil,  the  amount 
and  purity  of  the  water,  even  the  composition  and  density  of  the  atmos- 
phere, change  as  we  go  from  one  part  of  the  earth's  surface  to  another. 
So,  also,  light  is  intense  or  feeble,  and  temperature  high  or  low. 

Every  new  condition  requires  a  new  adjustment  of  the  running 
parts  of  the  machine.  It  is  peculiar  to  the  machines  which  we  call 
plants  and  animals  that  they  have  the  power  of  becoming  adjusted  to 
new  or  changed  conditions.  Even  in  the  individual  plant  there  is 
often  seen  a  certain  degree  of  the  capacity  for  accommodation.  When 
we  regard  generations  rather  than  individuals,  this  capacity  becomes 
still  further  apparent.  Finally,  when  we  look  at  the  whole  history  of 
plants  we  see  that  the  plasticity  of  the  plant  machine  is  in  the  long 
run  perfect  (within  certain  limits).  Thus,  plants  become  accustomed 
to  extremes  of  temperature.  Arctic  plants  remain  frozen  for  months 
without  harm.  At  a  temperature  very  near  the  freezing  point,  arctic 
and  mountain  plants  are  often  active.  On  the  other  hand,  tropical 
plants  resist  heat.  In  the  Punjab  (India),  air  temperatures  of  120° 
Fahr.  are  not  uncommon.  Schimper  states  that  in  a  hot  spring  of 
Venezuela  certain  low  Algae  thrive  at  above  176°  Fahr.  The  vegeta- 
ble machine,  then,  has  the  power  of  adapting  itself  in  the  course  of 
time  to  any  kind  of  heat  condition  within  the  absolute  death  limits. 
And  heat  is  taken  merely  for  illustration.  Adaptation  to  light  and 
shade,  or  to  variations  of  any  other  of  the  external  factors  of  plant 
existence,  might  have  been  given. 

Next,  it  is  to  be  noted  that  plants  of  very  different  kinds  often  be- 
come adapted  to  like  conditions  by  taking  on  much  the  same  structural 
1  "The  Mountains  of  California,"  by  John  Muir,  p.  181. 


THE  STEM  65 

features.  That  is,  the  general  type  of  machinery  that  serves  one 
species  under  given  conditions  comes  to  be  assumed  by  all  the  species 
living  under  the  same  conditions.  As  a  result  \ve  are  able  to  distin- 
guish certain  types  of  adaptation  prevailing  wherever  certain  sets  of 
conditions  are  found.  The  adaptation  is  seen  in  external  form  and  in 
internal  anatomy.  The  types  are  the  most  marked  where  the  condi- 
tions are  extreme. 

1.  The  Xerophytic  Type  is  exemplified  in  desert  plants.     The  ex- 
treme condition  is  scarcity  of  water.     The  plant  surfaces  from  which 
moisture  might  be  lost  (leaf  surfaces,  particularly)  are  in  these  plants 
reduced  to  the  smallest  limits.     See,  for  example,  Opuntia,  in  §  99, 
which   at  maturity  is   without   foliage    leaves.      A   similar  form   is 
exhibited  by  certain  Spurges  (Euphorbia)  and  Groundsels  (Senecio), 
quite  unrelated  plants.     The  internal  anatomy  is  characterized  by  the 
development  of  tissue  for  water  reservoirs,  and  of  a  thick  waterproof 
cuticular  covering  of  the  epidermis  (see  §  526). 

Between  the  extreme  desert  type  and  that  of  ordinary  plants  there 
are  all  gradations.  When  leaves  are  present  on  xerophytic  plants 
they  are  likely  to  be  leathery,  or  thick  and  succulent,  or  thickly  cov- 
ered with  hair ;  the  pores  (§  527)  are  sunken  in  the  thick  epidermis 
and  the  leaf  is  often  turned  edgewise  to  light  and  heat.  Xerophytic 
characters  are  found  in  plants  growing  in  dry  situations  in  ordinary, 
moist  climates. 

Other  causes  besides  dryness  of  soil  and  air  may  lead  to  scarcity  of 
water  in  the  plant,  at  particular  times  or  in  particular  locations.  In 
temperate  climates,  for  example,  the  winter  brings  frozen  soil,  and 
consequent  arrest  of  absorption  at  the  root.  Hence,  the  plants  are 
placed  temporarily  in  xerophytic  conditions,  and  most  perennials  meet 
the  emergency  by  the  loss  of  leaves.  So,  also,  the  coldness  of  far 
northern  and  high  mountain  soils  produces  a  condition  of  drought, 
with  the  resultant  appearance  of  xerophytic  characters  in  the  vegeta- 
tion. Root  absorption  may  also  be  diminished  by  the  presence  of 
salts  dissolved  in  large  quantities  in  the  water  about  the  root.  Such 
an  effect  is  wrought  in  salt  marshes,  and  on  sea  shores  above  the  tide, 
where  the  plants  show  characteristic  xerophytic  adaptations.  Plants 
fitted  to  life  in  such  conditions  are  termed  Halophytes. 

2.  The  Hydrophytic  Type. — Submerged  plants,  and  such  as  grow 
largely  submerged  in  fresh  water,  are  in  general  characterized  by  a 
thin  epidermis,  weak  development  of  the  framework,  and  large  air 
passages  traversing  the  entire  plant  body.     These  interspaces  allow 
the  penetration  of  air  for  respiration  to  submerged  parts,  as  well  as 
give  buoyancy  to  floating  parts.    For  characteristic  forms  of  the  leaves 
see  §§  130-135. 

2.  The  Mesophytic  Type  of  structure  is  that  of  plants  living  under 
ordinary  conditions.  The  common  tillage  plants  are  Mesophytes. 

OUT.   OK  BOX 6 


66  STUDIES   OF  THE  LEAF 

It  must  be  understood  that  the  terms,  Xerophyte,  Hydrophyte, 
Mesophyte,  are  merely  abstract  designations  for  general  types  of 
adaptation.  When  we  say  Xerophyte,  we  mean  any  plant  showing 
adaptation  to  a  dry  habitat.  The  same  plant  may  be  at  different 
periods  of  the  year  mesophytic  (as  the  Maple  or  Elm  in  summer)  and 
xerophytic  (as  the  same  tree  in  winter). 

IX.    LABORATORY  STUDIES  OP  THE  LEAF 
EXERCISE  XXIII.     THE  ACTIVITIES  OF  THE  LEAF 

Experiment  n.  —  Select  a  healthy  green  Nasturtium  plant.  Place 
it  in  darkness  for  three  days.  Then  cut  one  or  two  leaves,  boil  them  in 
water,  decolorize  them  in  strong  alcohol  (this  may  take  a  day  or  so), 
and  then  treat  with  iodine  to  determine  the  presence  or  absence  of 
starch. 

Meanwhile,  when  the  plant  is  first  taken  from  darkness,  cover  a  part 
of  one  of  the  leaves  in  the  following  manner  :  Cut  disks  from  a  cork 
stopper ;  place  them  on  opposite  sides  of  the  leaf ;  stick  two  pins  through 
both  corks  and  leaf,  to  hold  the  corks  in  place.  A  portion  of  one  leaf 
being  thus  entirely  darkened,  expose  the  plant  for  at  least  a  day  in 
sunlight.  Then  test  two  or  three  of  the  leaves,  including  the  partly 
darkened  one,  for  the  presence  or  absence  of  starch,  in  the  same  man- 
ner as  before  directed.  Compare  with  the  former  results. 

Where  is  starch  formed  in  plants?  What  is  one  condition  of  its 
production,  as  determined  by  this  experiment  ?  (There  are  other  con- 
ditions.)1 

Experiment  12.  —  Pour  a  little  water  into  a  fruit  jar,  enough  to 
cover  the  bottom.  Put  in  a  few  leaves,  with  their  stalks  in  the  water. 
Put  in,  also,  a  small  beaker  with  limewater.  Close  the  jar  tightly. 
Place  the  jar  in  the  dark. 

Arrange  a  second  jar,  water  and  limewater,  without  leaves,  and 
place  it  beside  the  first. 

After  twenty-four  hours  examine  the  limewater  in  both  beakers  for 
the  action  of  carbon  dioxide,  as  in  the  experiment  on  respiration  of 
germinating  seeds. 

Experiment  13.  —  Select  a  plant  with  a  single  stem  below,  bearing  a 
good  number  of  leaves.  Wrap  the  pot  in  sheet  rubber,  which  is  to 
be  brought  up  around  the  stem  of  the  plant  and  securely  tied.  The 
evaporation  of  water  from  the  pot  and  soil  is  thus  prevented. 

Weigh  the  plant  as  thus  fixed,  and  record  both  weight  and  time. 
In  doing  this,  set  the  scales  in  the  sun  if  possible,  and  having  found 

1  Experiment 6,  from  Ganong's  "Teaching  Botanist,"  may  well  he 
introduced  here  if  the  apparatus  is  available.  See  also  Appendix,  where 
important  experiments  are  recommended. 


STUDIES   OF  THE  LEAF 


67 


the  weight,  leave  the  plant  counterbalanced  on  the  scales.  In  a 
relatively  short  time  it  will  be  seen  whether  the  plant  gains  or 
loses. 

Set  the  plant  in  a  sunny  or  well-lighted  place.  If  possible  weigh 
again  some  hours  later  the  same  day ;  if  not,  the  next  day.  Record 
weight  and  time. 

Let  the  plant  now  remain  in  darkness  as  nearly  as  possible  an  equal 
length  of  time.  Again  weigh,  and  record  weight  and  time. 

What  has  caused  the  change  of  weight?  (Before  the  answer  is  re- 
quired, the  next  experiment  will  naturally  have  been  done;  there  will 
be  additional  reason  to  assign  the  change  of  weight  to  one  particular 
cause.)  What  effect  has  light  upon  the  rate  of  change? 

Experiment  I4.1  —  Two  tumblers,  a  piece  of  pasteboard,  a  piece  of 
sheet  rubber  large  enough  to  cover  the  mouth  of  the  tumbler,  and  a 
leaf,  are  needed.  One  tumbler  is  nearly  filled  with  water.  The  paste- 
board, with  a  hole  in  it,  is  placed  on  this  tumbler.  A  puncture  is 
made  in  the  middle  of  the  rubber,  the  rubber  stretched,  and  the  leaf- 
stalk put  through  the  puncture.  The  leaf  is  now  put  on  the  tumbler, 
its  stalk  descends  into  the  water  through  the  hole  in  the  pasteboard. 
The  blade  of  the  leaf  is  now  covered  with  the  second  tumbler,  and  the 
apparatus  set  in  the  sun. 

In  a  few  minutes  an  effect,  due  to  the  activity 
of  the  leaf  under  the  influence  of  light  and  heat, 
should  be  seen. 

Experiment  15.  —  Relative  activity  of  the 
upper  and  under  sides  of  the  Begonia  leaf. — 
Two  dry  watch  glasses  are  to  be  placed  on  oppo- 
site sides  of  a  Begonia  leaf  (still  on  the  plant) 
and  held  in  place  by  a  clip,  or  by  two  wooden 
strips  and  elastic  bands,  as  in  the  figure.  Two 
inclosed  spaces  are  thus  made,  on  the  under  and 
upper  faces  of  the  leaf  respectively.  Neither 
should  be  in  direct  sunlight.  Examine  the 
watch  glasses  for  a  deposition  of  moisture  after 
fifteen  or  twenty  minutes,  or  longer.  Which  side 
of  the  leaf  exhales  moisture  the  more  rapidly? 

Experiment  16. —  Secure  two  mature  leaves 
of  the  India  Rubber  Plant  (Ficus  elastica). 
After  smearing  the  under  face  of  one  and  the 
upper  face  of  the  other  with  vaseline,  as  well  as  the  cut  end  of  the  leaf 
stalk  in  each  case,  so  as  to  prevent  the  escape  of  moisture  from  these 
surfaces,  hang  the  two  leaves  side  by  side  to  dry.  When  either  one  is 

1  Experiments  14, 15,  and  16  may  be  given  to  different  pupils,  or  groups, 
simultaneously,  as  one  or  two  preparations  of  each  experiment  will  serve 
for  a  whole  class  or  division. 


54.  Method  of  holding 
watch  glasses 
(w)  upon  Begonia 
leaf. 


68  STUDIES   OF  THE  LEAF 

considerably  dried,  record  the  result  and  the  conclusion  as  to  which 
surface  exhales  vapor  more  freely. 

Experiment  17. —  A  growing  plant  of  Nasturtium,  which  has  been 
standing  for  several  hours  in  one  position  so  that  the  light  lias  steadily 
come  from  one  direction,  is  to  be  observed.  Do  all  the  leaves  face  in 
one  direction  ?  Or  several  leaves  ?  If  so,  mark  the  side  of  the  pot 
toward  which  they  incline  with  some  distinctive  mark  (e.g.,  A.B.  9.80). 
Young  leaves,  or  at  least  those  not  declining  in  vigor,  should  be  chosen 
for  record.  In  the  notebook  record  the  position  of  one  of  these  leaves 
diagrammatically,  as  seen  from  above.  The  diagram  will  consist  of  a 
circle,  for  the  pot;  a  radial  line  (marked  le),  for  the  petiole  of  the 
selected  leaf;  a  line  across  the  end  of  this,  for  the  blade;  and  an 
arrow  (marked  li)  outside  the  circle,  for  the  direction  of  the  principal 
body  of  light. 

Note  the  attitude  of  the  stem,  as  seen  from  the  marked  side  of  the 
pot.  Represent  it  by  a  diagram:  make  a  straight  level  line  for 
the  rim  of  the  pot;  another  rising  from  this,  for  the  stem.  Record 
the  time.  Now  expose  the  plant  to  strong  light  from  a  new  direction. 
Indicate  this  on  the  first  diagram  by  a  second  arrow  (li'}- 

Leave  till  a  change  is  plain.  At  length  indicate  the  position  of  the 
selected  leaf  by  new  lines  (le')  on  diagram  1,  and  the  attitude  of  the 
stem,  as  seen  from  the  original  side  of  observation,  by  a  dotted  line  on 
diagram  2.  If  any  movements  of  leaf  blades  are  discovered,  find  how 
far  they  are  due  to  the  curvings  of  the  petioles. 

Experiment  18.  —  So-called  sleep  movements. 

Note  the  position  of  the  leaflets  on  seedlings  of  the  Sensitive  Plant 
(Mimosa  pudica)  when  standing  in  the  light.  Now  place  over  the  pot 
carefully,  without  jarring  the  plants,  a  box  or  blackened  bell  jar,  so  as 
to  exclude  all  light.  In  fifteen  minutes  or  so,  uncover  carefully. 
What  change  in  the  position  of  the  leaves?  Oxalis  may  be  used  for 
this  experiment.  If  Lupine  or  Bean  is  used,  the  time  will  be  longer. 
They  may  be  left  in  a  dark  closet  over  night. 

Experiment  19.  —  Sensitiveness  of  Mimosa. 

Use  the  seedlings  of  the  last  experiment.  Touch  one  of  the  leaflets 
very  gently.  Touch  others  less  gently.  Note  the  several  effects  in  any 
one  leaf,  and  if  they  occur,  the  resulting  effects  on  surrounding  leaves. 
Are  the  cotyledons  sensitive?  Select  a  plant  which  is  still  in  the 
normally  expanded  condition.  Press  a  hot  needle  against  one  of  the 
cotyledons,  without  shaking  the  plant.  Wait  for  the  effect. 

If  a  large  plant  is  available,  apply  a  match  flame  to  the  tip  of  one  of 
the  leaves.  Note  what  parts  are  affected  in  succession,  and  the  manner 
in  which  the  effect  travels  over  the  plant.  Measure  the  greatest  distance 
to  which  the  effect  is  transmitted,  and  the  time  taken  in  transmission. 

This  experiment  may  be  done  before  the  whole  laboratory  division, 
one  plant  serving  for  all.  If  time  and  facilities  permit,  it  will  be  of 


STUDIES  Of  THE  LEAF  69 

interest  to  determine  the  effect  of  low  temperature  on  the  sensitiveness 
of  the  plant ;  temperature  between  40°  and  50°,  for  instance,  to  which 
the  plant  has  been  exposed  for  a  few  hours.  The  effect  of  varying  the 
humidity  of  the  surrounding  air  may  be  ascertained  by  keeping  some 
well-moistened  young  plants  under  a  bell  jar,  and  comparing  with 
others  kept  in  a  very  dry  place. 

EXERCISE  XXIV 

(1)  The  parts  of  a  typical  leaf.  —  Draw  the  given  leaf  in  simple 
outline  to  show  the  blade;  the  petiole,  or  stalk;  the  stipules  (a  pair  of 
members  at  the  base  of  the  petiole,  like  leaflets). 

(2)  The  structure  of  the  blade  1  —  Examine  the  blade  under  the  lens 
by  transmitted  light,  shielding  it  from  direct  light. 

NOTE  :  —  («)    The  translucence. 

(6)    The  distribution  of  the  green  color. 
(c)    The  relative  thickness  of  the  ribs  and  the  rest  of  the 
blade  (use  direct  light). 

Trace  the  main  framework  of  one  half  of  the  leaf,  including  in  the 
drawing  only  the  most  prominent  ribs  and  their  conspicuous  connect- 
ing veins. 

How  many  ranks  or  orders  of  ribs  and  veins  do  you  distinguish  ? 
Determine  this  as  follows :  Follow  the  midrib,  then  one  of  its  large 
branches,  then  one  of  the  main  branches  from  this,  —  and  so  on ; 
counting  the  number  of  turns  made  to  arrive  at  the  smallest  veinlet's 
end. 

Draw  a  small  square  to  show  the  veinlets  of  the  two  or  three  lowest 
ranks,  as  seen  through  the  lens. 

Experiment  20.  —  Place  a  leaf  with  its  stalk  in  water  colored  with 
eosin,  and  later  trace  the  water  courses  of  the  leaf. 

Experiment  21.  —  Take  a  wilted  leaf,  and  after  noting  with  care  how 
flaccid  it  is,  put  it  entirely  under  water  for  a  day.  Then  note  again 
the  degree  of  rigidity. 

Does  contained  water  play  any  part  in  the  support  and  stability  of 
the  leaf  blade?  2 

EXERCISE    XXV 

Take  a  shoot  of  the  Pea  three  or  four  weeks  old  at  least,  with  several 
leaves  fully  formed  and  a  growing  bud. 

Note  the  stipules.  Where  is  the  growing  tip  of  the  shoot,  and  how 
is  it  protected?  What  two  uses  do  the  stipules  here  subserve?  The 

1  For  the  minute  structure  see  Chapter  XVII. 

2  To  determine  whether  in  this  experiment  water  is  taken  up  readily 
through  the  general  surface,  use  several  uninjured  leaves,  some  of  which 
have  the  petioles  raised  above  water. 


70  STUDIES  OF  THE  LEAF 

lateral  tendrils  occupy  the  same  relative  positions  on  the  main  axis 
(or  rhachis)  of  the  leaf  as  what  other  parts?  What  is  the  morphology 
of  the  lateral  tendrils?  What  three  very  distinct  and  different  offices 
does  the  leaf  of  the  Pea  fulfill  ? 

Draw  the  entire  leaf  with  its  parts  labeled.  Show  (by  another 
drawing  if  necessary)  the  mode  of  protecting  the  bud;  indicate  the 
position  of  the  bud  by  dotted  lines. 

EXERCISE  XXVI.     TYPES  OF  VENATION 

Consider  the  character  of  the  veining,  and  the  arrangement  or  plan 
of  the  framework,  in  the  given  leaves. 

Compare  and  assort  the  leaves.  Divide  them  into  groups  according 
to  the  similarities  and  differences  in  these  respects. 

Draw  the  margins  and  main  structure  lines  of  the  several  leaves 
(half  the  leaf  will  show  the  points  wanted). 

After  the  notes  covering  the  above,  write  a  concise  description  of 
each  leaf,  under  the  headings  (1)  Venation,  (2)  General  Shape, 
(o)  Margin,  (4)  Apex,  (5)  Base ;  referring  to  pages  77,  78,  and  92-96 
of  this  book  for  the  proper  terms. 

EXERCISE  XXVII.     COMPOUND  LEAVES 

To  which  of  the  types  of  frame  plan,  studied  in  the  last  exercise, 
does  each  of  the  compound  leaves  correspond,  in  the  arrangement  of 
its  leaflets  ?  Are  the  leaflets  jointed  to  the  main  stalk  ? 

Draw  the  given  leaves  in  simple  outline.  Label  each  with  the 
proper  descriptive  term  (see  pages  96-99). 

EXERCISE   XXVIII.      SPECIAL   USES  OR   MODIFICATIONS   OF   THE 

LEAF 

Barberry.  —  Study  the  leaves  subtending  the  lateral  buds  or  leaf 
clusters  on  a  shoot  of  barberry.  What  is  the  use  of  these  leaves  ? 

Draw  two  or  three  examples  to  show  transition  from  the  foliage  to 
the  spinelike  condition. 

Onion.  —  The  material  suggested  is  the  Onion  "  set,"  or  young  bulb, 
slightly  sprouted.  Note  the  outer,  thin  scales,  —  for  what  purpose  are 
they  formed  ?  What  are  they  morphologically  ?  Cut  the  bulb  in  half, 
lengthwise.  Study  the  parts.  Note  the  stem,  producing  roots,  and 
leaves.  Some  of  the  outer  leaves  are  thickened,  and  do  not  extend 
upward.  What  is  their  use? 

Draw  the  longitudinal  section  of  the  bulb,  somewhat  enlarged. 

Foliage  of  Acacia  (Optional).  —  What  is  the  morphology  of  the  flat, 
green  appendages  of  the  stern?  Answer  after  noting  (a)  their  posi- 
tion on  the  stem,  (&)  direction  in  which  the  surfaces  look,  whether  to 


THE  LEAF  71 

sky  and  earth  like  normal  leaf  blades,  or  to  right  and  left.  Do  they 
belong  to  the  class  of  leaf  formations  or  that  of  modified  stems  ?  They 
represent  how  much  stem?  leaf? 

Draw  the  body  in  question,  with  enough  of  the  stem  to  show  the 
position. 

X.    THE  LEAP 

103.  We  have  seen  that  as  soon  as  the  seedling  comes 
up  the  cotyledons  are  spread,  and  the  leaves  of  the  plumule, 
if  already  formed,  are  shortly  unfolded  to  catch  the  sun- 
light;  and  that  even  within  the  first  day  after  emerging 
from  the  soil,  the  leaves  of  the  seedling  take  on  a  deep 
green  color,  the  sign  of  healthy  activity  in  plants.     In 
buds,  leaves  have  been  studied  in  their  early  stages  and 
in  the  resting  condition ;    and  it  has  been  seen  how  both 
above-ground  and  beneath-ground  leaves  are  prepared  long 
before  they  are  needed  as  foliage,  and  are  held  in  reserve  in 
order  that  upon  the  return  of  warm  weather  in  the  spring 
the  plants  may  begin  with  little  delay  to  make  new  growth. 
The  varied  developments  of  the  stem,  as  rigid  shafts  of 
great  height,  as  twining  or  as  climbing  stems,  have  the 
object  of  displaying  the  leaves  to  the  light  to  the  best 
advantage.     All  these  things  point  to  the  activity  of  the 
leaf  in  carrying  on  vegetable  life. 

THE   OFFICE   OF   THE  LEAF 

104.  The  leaf  is  doubly  active  in  nourishing  the  plant. 
In  the  first  place,  it  absorbs,  like  the  root ;  only,  while 
the  root  takes  up  liquids  and  solutions,  the  leaf  takes  in 
gases.     Secondly,  the  leaf  is  especially  the  organ  in  which 
solar  energy  is  caught  and  stored  by  the   formation   of 
certain  substances.     These  substances  are  the  food  of  the 
plant,  —  using  now  the  word  food  in  the  same   sense  in 
which  it  was  used  in  the  chapter  on  seeds  and  seedlings. 
The  food  formed  in  the  leaf  contains  energy  to  be  used 
in  growth  and  motion. 

105.  The  food  provided  for  the  seedling  by  the  mother 
plant  is  of  small  amount.     Very  soon  after  germination 


72  rY    tHE  LEAF 


the  seedling  HI  Ustieed  itself.  In  the  soil  there  is  no 
supply  of  starch,  oil,  sugar,  or  the  like,  or,  if  there  is  a 
small  proportion  of  these  matters  present  through  the 
decay  of  former  vegetation,  yet  these  would  not  be  enough 
to  furnish  material  for  all  the  new  plants  that  grow.  If 
there  is  none  at  all,  —  if,  for  example,  we  grow  the  seedling 
in  clear  sand  watered  with  distilled  water,  with  the  addi- 
tion merely  of  a  few  mineral  salts  in  very  small  quantity, — 
the  young  plant  grows  perfectly  well.  In  other  words,  it 
is  able  to  form  its  own  food.  This  food  it  makes  largely 
through  the  agency  of  its  leaves. 

106.  Soil  and  air  furnish  the  raw  materials.     These  are 
water,  sucked  up  by  the  root,  and  carbonic  acid  gas  (car- 
bon dioxide),  absorbed  by  the  leaf  from  the  atmosphere. 
These  two  meet  in  the  soft  green  tissue  of  the  leaf.     By 
the  power  of  sunlight,  in  the  presence  of  chlorophyll  (the 
green  coloring  matter),  the  water  and  the  gas  are  decom- 
posed, and  their  elements  recombined  in  such  a  manner 
that  a  solid  makes  its  appearance  ;  namely,  starch.     Starch 
is  in  its  nature  very  like  the  living  substance  itself,  and 
may  be  used  in  growth.     It  is  then  food,  in  the  most 
appropriate  sense  of  the  word.     Water,  carbon  dioxide, 
and  small  quantities  of  other  substances,  since  they  can  be 
added  only  indirectly  to  the  living  substance,  are  not  food 
in  the  same  sense  as  starch. 

107.  The  formation  of  organic  substance   (as  starch) 
from  these  raw  materials  is  called    carbon   assimilation ; 
when  brought  about  through  the  agency  of  light,  as  in 
all  ordinary  cases,  it  is  called  photosynthesis. 

FORM  AND  QUALITIES  OF  THE  LEAF 

108.  The  form  of  the  leaf  results  from  its  use.     Thin- 
ness gives  full  exposure  to  light  and  good  aeration.     The 
leaf  is  translucent  as  well  as  thin,  so  that  all  parts  of  the 
tissue  are  reached  by  the  energizing  rays.     It  is  compara- 
tively strong  and  elastic,  —  qualities  given  by  the  woody 
framework   of   ribs  and  veins.     The   strengthening   ele- 


THE  LEAF 


73 


Leaf  of  the  Quince ; 
b,  blade;  p,  peti- 
ole ;  st,  stipules. 


ments  are  also  conduits  of  water  and  of  the  prepared  plant 
food  when  this  is  drawn  away  from  the  leaf  in  a  liquid 
form  to  other  parts  of  the  plant.  The  smallest  veinlets 
penetrate  to  every  section  of  the  active  green  tissue,  assur- 
ing an  abundance  of  water.  That  water  throughout  the 
whole  body  of  the  leaf  plays  an  important  part  in  keeping 
the  leaf  elastic  and  outspread  is  seen  when,  from  lack  of 
watering,  the  leaves  of  plants  wilt  and 
droop. 

109.  The  parts  of  the  leaf. — When 
most   highly  developed,    the   leaf   has 
three    parts,  —  the  petiole,   or   stalk,   a 
pair  of  stipules  at  the  base  of  the  peti- 
ole, and  the  blade,  or  lamina  (Fig.  55). 

110.  Stipules.  —  In  the  majority  of 
leaves  stipules   are    quite  wanting;  if 
produced  at  all,  they  are  in  many  cases 
soon  lost.     In  the  Pea,  however,  where 

the  terminal  part  of  the  blade  is  converted  into  a  tendril, 
the  stipules  are  large  and  take  part  in 
assimilation.  Ordinarily,  the  stipules 
originate  when  the  leaf  is  very  small, 
attain  their  growth  early,  and  overarch 
and  protect  the  young  and  tender  blade  ; 
or,  as  in  Begonia  (Fig.  15),  the  stipules 
of  each  leaf  regularly  inclose  and  shield 
the  younger  leaves  of  the  shoot.  In  very 
many  winter  buds  the  scales  are  of  the 
nature  of  stipules.  The  chief  use  of 
stipules  is,  then,  protective. 

111.  A  special  modification  of  stipules  to  serve 
quite  other  uses  is  seen  in  the  case  of  the  prickles 
of  the  Locust  (Fig.  56). 

112.  In   Acacia  spadicigera  the  stipules  are 
the    developed  as  hollow  thorns,  an  inch  or  more  in 

length,  which  become  the  dwelling  places  of  cer- 
kles.  tain  small  and  exceedingly  warlike  ants.    At  the 

ends  of  the  leaflets  this  Acacia  bears  small  food 
bodies,  rich  in  fat,  and  in  special  glands  secretes  nectar.     These  mate- 


74 


THE  LEAF 


rials  constitute  the  food  of  the  thorn-inhabiting  ants,  for  whose  sub- 
sistence the  tree  seems  thus  definitely  to  provide.  In  return  the 
warlike  ants  defend  the  Acacia  from  animal  foes,  in  particular  from 
leaf-cutting  insects. 

113.  The  petiole.  —  The  petiole  is  sometimes  lacking-, 
and  in  this  case  the  leaf  is  said  to  be  sessile.  The  gen- 
eral office  of  the  petiole  is  to  aid  in  securing  the  best  posi- 
tion for  the  blade  in  respect  to  light.  This  it  would  do 
merely  by  its  length,  since  the  space 
available  for  all  the  leaves  around  the 
stem  is  increased  in  proportion  to  the 
length  of  the  petioles.1  But  further 


58.  A  prostrate  shoot  of  Galium.  The  leaves  now  dis- 
pose themselves  in  horizontal  positions,  and  with- 
out much  over-shading  of  one  by  another. 


57.  An  erect  shoot  of 
Galium.  The 
whorled  leaves 


ahout     equally 


than  this  the  petiole,  by  its  own  move- 
ment,  so    disposes    the    blade    that    it 

*- 

receives  the  best  illumination  possible 
under  anJ  Siven  circumstances  (Figs. 
57,  58).  If  a  potted  plant,  not  too  old, 
is  taken  from  a  position  where  it  has 
been  lighted  from  above  or  on  all  sides,  and  placed  at  a 
little  distance  from  the  window  in  a  room  where  the  light 
enters  only  at  one  side,  and  the  plant  is  closely  watched, 
it  will  shortly  be  seen  that  nearly  all  the  leaves  are  very 
slowly  moving.  The  whole  plant  indeed  seems  to  be 
alive  to  the  new  direction  of  light  and  gradually  turns 
its  leaves  in  that  direction.  This  result  is  effected  by 
the  leaf  stalks,  though  young  portions  of  the  stem  are 
pretty  sure  to  take  part  in  the  general  movement. 

1  Strictly  the  area  in  any  one  plane  is  proportional  to  the  square  of  the 
length  of  the  lines.  If  the  petioles  are  doubled  in  length,  the  space  avail- 
able for  the  blades  becomes  quadrupled. 


THE  LEAF  75 

114.  At  the  junction  with  the  blade  and  at  the  base, 
next  to  the  stem,  portions  of  the  petiole  may  possess  a 
special  structure  by  which  more  or  less  rapid  movements 
are  secured  when  the  blade  is  stimulated  through  con- 
tact or  injury  or  by  changes  in  the  intensity  of  light. 
These  portions,  marked  off  from  the  rest  of  the  petiole 
and  often  somewhat  swollen,  are  called  pulvini  (singular, 
pulvinus).     They  are  well   seen  in  the  Bean  and  other 
plants  of  the  same  family. 

115.  Of  periodic  movements  executed   by  the  action  of 
the   petiole,    the    "  sleep "  move- 
ments of  numerous  plants  are  to 

be  noted.  Figure  59  represents 
the  leaflets  of  the  White  Lupine 
at  night.  The  blade  is  here 
divided  into  five  or  more  parts, 
or  leaflets.  Each  has  a  short 
stalk,  or  petiolule.  When  day- 
light fails,  the  petiolules  bend 
more  or  less  sharply  downward. 
When  this  action  is  most  vigor- 
ous, as  in  some  of  the  younger 
leaves,  the  leaflets  are  brought  59.  The  "  si- of  the  White 
closely  together ;  and  they  are 
retained  in  this  position  with  some  force.  With  the  return 
of  daylight  the  petiolules  are  stimulated  to  elevate  the 
leaflets  again.1 

116.  When  the  cotyledons  of   seedlings  exhibit  sleep 
movements,   they  usually   fold  upward,  the   inner  faces 
approaching  each  other  more  or  less  closely. 

117.  It   must  not   be   supposed  that  the  lowering   of 
leaves  or  leaflets  in  such  cases  is  an  act  of  resting  on  the 
part  of   the   plant ;    although    Linnseus   gave   the   name 

lrTry  the  effect  of  keeping  seedlings  of  Clover,  Oxalis,  Bean,  or 
Lupine  in  the  dark  until  late  in  the  forenoon,  or  even  all  day.  Are  the 
sleep  movements  habitual  or  effected  only  in  response  to  change  of  illu- 
mination ?  Is  lamp  light  or  electric  light  bright  enough  to  wake  sleeping 
plants  ? 


76  THE  LEAF 

"  Sleep  of  Plants"  to  all  such  movements  from  the  evident 
suggestion  of  rest.  A  definite  advantage  is  gained  by 
the  nocturnal  position.  The  surfaces  of  the  blades  being 
vertical,  or  nearly  so,  and  the  several  leaflets  brought  to- 
gether in  a  cluster  (in  the  case  of  compound  leaves),  there 
is  less  likelihood  that  the  leaves  will  be  chilled  or,  in  cool 
climates,  frost-bitten. 

118.  The  "Sensitive  Plant."  —  The  most  striking  exhibition  of 
leaf  movements  after  stimulation  is  perhaps  given  by  the  house  plant, 
known   from  its  peculiar  behavior  as  the  Sensitive  Plant  (Mimosa 
pudicd).      The  merest  touch  on  one  of  the  leaflets  causes  the  suc- 
cessive closing  together  of  all  the  neighboring  leaflets,  or  perhaps  all 
parts  of  the  entire  leaf.     If  the  shock  is  slightly  increased,  the  effect 
may  not  only  traverse  the  entire  leaf  and  cause  it  to  droop  on  the 
stem,  but  be  transmitted  to  the  other  leaves  as  well.1 

119.  Leaves  without  blades.  —  fn  a  few  cases  the  blade  of  the  leaf 
is  quite  lacking,  while  its  place  is  supplied  by  the  enlarged  and  flat- 
tened petiole.     Certain  Acacias  of  Australia  normally  have  no  other 

foliage.  In  the  seedling, 
however,  leaves  appear 
bearing  blades.  As  the 
seedling  grows  older,  the 
petioles  of  these  bladed 
leaves  are  seen  to  be  flat- 
tened. Finally  the  blades 
fail  altogether,  on  leaves 
produced  at  a  little  later 
60.  Terminal  portion  of  the  shoot  of  a  seed-  .  stage,  only  phyllodes  (phyl- 

ling  Acacia:  1,  the  last  of  the  seedling     iodia\  ai)Dearino.  rFis-  60^ 

leaves  to  show  true  blades;    2  and  3, 

bladeless,  flattened   petioles,  or  phyl-     Tne  flattening  is  vertical, 

lodes.  so  that  the  phyllode  (phyl- 

lodium)  presents  its  edges 

to  earth  and  sky.  This  fact,  even  in  the  total  absence  of  blade  or 
blades,  would  distinguish  these  formations  from  normal  leaf  blades. 

The  Blade 

120.  Framework  and  venation.  —  The  framework  consists  of  wood, 
—  a  fibrous  and  tough  material  which  runs  from  tne  stem  through  the 

1  The  most  remarkable  effects  are  produced  by  applying  a  flame,  as  a 
match  flame,  to  one  of  the  terminal  leaflets.  The  impulse  to  contraction 
may  often  be  followed  from  one  leaf  to  another  over  the  whole  plant. 
Measure  the  greatest  distance  to  which  the  stimulus  is  transmitted. 


THE  LEAF 


77 


leaf  stalk,  when  there  is  one,  in  the  form  of  parallel  threads  or  bundles 
of  fibers ;  and  in  the  blade  these  spread  out  in  a  horizontal  direction, 
to  form  the  ribs  and  veins  of  the  leaf.  The  stout  main  branches  of 
the  framework  are  called  the  ribs.  When  there  is  only  one,  as  in 
Fig.  61 ,.  or  a  middle  one  decidedly  larger  than  the  rest,  it  is  called  the 
midrib.  The  smaller  divisions  are  termed  veins;  and  their  still 
smaller  subdivisions,  veinlets.  The  latter  subdivide  again  and  again, 
until  they  become  so  fine  that  they  are  invisible  to  the  naked  eye.  The 
fibers  of  which  they  are  composed  are  hollow ;  forming  tubes  by  which 
the  sap  is  brought  into  the  leaves  and  carried  to  every  part. 

121.  Venation  is  the  name  of  the  mode  of  veiniug;  that  is,  of  the 
way  in  which  the  veins  are  distributed  in  the  blade.     This  is  of  two 
principal  kinds;  namely,  the  parallel-veined,  and  the  netted-veined. 

122.  In    netted-veined    (also    called   reticulated)    leaves,   the  veins 
branch  off  from  the  main  rib  or  ribs,  divide  into  finer  and  finer  vein- 
lets,  and  the  branches  unite  with  each  other  to  form  meshes  of  network. 
That  is,  they  anastomose,  as  anatomists 

say  of  the  veins  and  arteries  of  the  body. 
The  Willow  leaf,  in  Fig.  61,  shows  this 


Reticulated  venation  of  a 
Willow  leaf.  —  ETTINGS- 

HAUSEN. 


62.  Parallel  venation  of  the 
Lily  of  the  Valley  leaf. 
—  ETTINGSHAUSEN. 


kind  of  veining  in  a  leaf  with  a  single  rib.     The  Maple,  Basswood, 
and  Plane  or  Buttonwood  show  it  in  leaves  of-  several  ribs. 

123.  In  parallel-veined  leaves,  the  whole,  framework  consists  of 
slender  ribs  or  veins,  which  run  parallel  with  each  other,  or  nearly  so, 
from  the  base  to  the  point  of  the  leaf,  —  not  dividing  and  subdividing, 
nor  forming  meshes,  except  by  minute  cross  veinlets.  The  leaf  of  any 
grass  or  that  of  the  Lilly  of  the  Valley  (Fig.  62)  will  furnish  a  good 


78  THE  LEAF 

illustration.  Such  parallel  veins  Linnaeus  called  nerves,  and  parallel- 
veined  leaves  are  still  commonly  called  nerved  leaves,  while  those  of 
the  other  kind  are  said  to  be  veined,  — terms  which  it  is  convenient  to 
use,  although  these  "nerves"  and  "veins"  are  all  the  same  thing,  and 
have  no  likeness  to  the  nerves  and  little  to  the  veins  of  animals. 

124.  Netted-veined  leaves  belong,   with  comparatively  few  excep- 
tions, to  the   dicotyledonous  plants;    while   parallel-veined  or  nerved 
leaves  belong  in  general  to  the  Monocotyledons.     So  that  a  mere  glance 
at  the  leaves  generally  tells  what  the  structure  of  the  embryo  is,  and 
refers  the  plant  to  one  or  the  other  of  these  two  grand  classes.     For 
when  plants  differ  from  each  other  in  some  one  important  respect, 
they  usually  differ  correspondingly  in  other  respects  also. 

125.  Parallel-veined  leaves  are  of  two  sorts,  —  one  kind,  and  the 
commonest,  having  the  ribs  or  nerves  all  running  from  the  base  to 
the  point   of   the   leaf,  as   in  the  examples  already  given ;    while  in 
another  kind  they  run  from  a  midrib  to  the  margin,  as  in  the  common 
Pickerel  weed  of  our  ponds,  in  the  Banana,  in  Calla,  and  many  similar 
plants  of  warm  climates. 

126.  Netted-veined  leaves  are  also  of  two  sorts,  as  in  the  examples 
already  referred  to.     In  one  case  the  veins  all  rise  from  a  single  rib 
(the  midrib),  as  in  Fig.  61.     Such  leaves  are  called  feather-veined  or 
pinna^ej^v^ined^;  both  terms  meaning  the  same  thing,  namely,  that 
the  veins  are  arranged  on  the  sides  of  the  rib  like  the  plume  of  a 
feather  on  each  side  of  the  shaft. 

127.  In  the  other  case  (as  in  Fig.  15),  the  veins  branch  off  from 
three,  five,  seven,  or  nine  ribs,  which  spread  from  the  top  of  the  leaf- 
stalk, and  run  through  the  blade  like  the  toes  of  a  web-footed  bird. 
Hence  these  are  said  to  be  palmately  or  digitately  veined,  or  (since  the 
ribs  diverge  like  rays  from  a  center)  radiate-veined. 

128.  Since  the  general  outline  of  leaves  accords  with  the  frame- 
work or  skeleton,  it  is  plain  that  feather-veined  leaves  will  incline  to 
elongated  shapes ;  while  in  radiate-veined  leaves  more  rounded  forms 
are  to  be  expected. 

129.  The  shape  of  the  blade. — Infinite  variety  is  ex- 
hibited by  plants  as  regards  the  figure  of  the  blade.     Some 
of  the  chief  influences  to  which  the  forms  are  owing  are 
(1)  the  character  of  the  natural   surroundings,   (2)  the 
mode  of  folding  and  of  growth  in  the  bud,  and  (3)  the 
advantage  of  certain  shapes  in  respect  to  the  equal  illumi- 
nation of  all  the  leaves. 

130.  Natural  surroundings.  —  As  examples  of  the  influ- 
ence of  the  natural  surroundings,  or  habitat,  we  may  take 
aquatic  plants  with  submerged,  and  again   others   with 


THE  LEAF 


79 


floating,   leaves.      In  general,   submerged  plants  possess 

long  and  narrow,  or  linear,  leaves   (Fig. 

63).     Or,  they  may  have  leaves  of  a  more 

or  less  rounded  form,  but  much  divided, 

or   dissected,  into  linear  parts  (Fig.   64). 

Since   submerged  plants  of  many  widely 

separated   families  in   common   show  this 

type  of  leaf,  —  or  these  types, — the  form 

must  in  some  way  be  due  to  the  circum- 
stances of  life  in  water.  In  exactly  what 

respect  these  cir- 
cumstances call  for 
linear  leaf  forms 
is,  however,  an 
open  question. 
They  may  be  ad- 
vantageous from 
any  one  or  all 
of  the  following 
causes.  First, 
light  diminishes 
rapidly  as  depth 

of  water  increases.      It  will,  therefore,  be  an  advantage 

for  the  blade   to  reach  upward  as  far  as  possible  in  its 

growth ;  that  is,  to  take  a  linear  form. 

131.  Secondly,  the  narrow  and   dissected   forms   have 
been   attributed   to   the   scarcity  of   carbon  dioxide  and 
oxygen  in  water.      The  amount  of   these  necessary  sub- 
stances  that   will    be   absorbed   by  a   leaf,  other   things 
being  equal,  is  proportional  to  the  extent  of  the  surface 
in  contact  with  the  water.     The  more  divisions  the  leaf 
has,   or  the   longer  and  narrower  it  is,   the  greater  the 
surface  for  any  given  quantity  of  tissue ;  and  hence  the 
more  rapid  the  absorption  of  the  dissolved  gases. 

132.  In  the  third  place,  Sir  John  Lubbock  has  suggested 
that,  while  the   forms  under  discussion  do  offer  a  large 
amount  of  surface  relatively  to  the  total  mass  of  the  leaf, 
we  must  not  forget  that-  the  buoyancy  of  the  water  favors 


64.  One  of  the  submerged 
leaves  of  Cabomba,  a 
near  relative  of  the 
Water  Lily. 


63.  Fresh  water 

Eelgrass. 


80  THE  LEAF 

the  dissected  or  the  slender  conformation;  in  so  far  as  the 
water  supports  the  weight,  to  that  extent  a  compact  and 
rigid  framework  is  rendered  unnecessary.  He  compares 
such  leaves  as  those  of  Cabomba  (Fig.  64)  to  the  gills  of 
fishes,  which  while  in  water  float  apart,  but  have  not  enough 
strength  to  support  their  own  weight,  and  consequently 
collapse  in  air. 

133.  Finally,  it  is  evident  that  in  running  water  and 
in  waves  the  slender  forms  give  readily  to  the  movements 
of  the  water,  and  are  therefore  less  likely  to  be  torn  than 
broader  forms  would  be. 

134.  Floating  leaves  show  as  pronounced  a  tendency  to 
become  circular  as  the  submerged  ones  to  become  linear. 
The  circle,  or  ellipse,  may  be  complete  with  the  leaf  stalk 


65.  Floating  leaves :  a,  of  the  Water  Shield ;  6,  of  the  Water  Lily. 

running  to  the  center,  as  in  the  Water  Shield  (Fig.  65,  a). 
In  this  case,  the  form  is  said  to  be  peltate.  Or  the  circum- 
ference may  be  interrupted  by  a  cleft,  or  sinus,  leading  to 
the  summit  of  the  petiole  (e.g.  the  Water  Lily,  Fig.  65,  5). 
The  point  of  attachment  of  blade  and  petiole  is  the  real 
base  of  the  blade.  The  circle  is  filled  out,  in  fact,  by  the 
growing  backward  of  the  blade  at  each  side  of  the  base. 
This  leaf  is  described  as  orbicular,  and  cordate  (heart- 
shaped),  or  cordate  cleft,  at  the  base. 

135.  We  may  suppose  that  the  circle  is  the  most  advan- 
tageous form  in  leaf  building,  since  the  parts  are  equi- 
distant from  the  petiole,  and  thus  conduction  of  food 


THE  LEAF 


81 


matters  to  and  from  the  leaf  stalk  is  most  easily  per- 
formed; and  that  floating  leaves  are  free  to  acquire  this 
shape  because  they  do  not  overshade  one  another. 

136.  Again,  the  rounded  forms  are  plainly  better  bal- 
anced, ride  the  waves  better,  and  are  less  likely  to  be 
tipped  and  partially 
submerged.  It  is  im- 
portant that  the  upper 
surface  of  floating  leaves 
should  be  kept  free,  as 
is  shown  by  the  fact 
that  they  are  coated 
with  a  waxy  substance 
which  prevents  wetting, 
and  which  causes  water 
thrown  upon  the  leaves 
to  roll  away  in  all  direc- 
tions. The  pores  which 
admit  carbonic  acid  gas  «•  Leaf  °'  *e  Tulip  Tree  (Uriodendron). 
and  oxygen  are  in  this  upper  surface.  The  circular  blade 
with  the  petiole  attached  near  the  center  is  well  adapted 
to  keeping  every  part  afloat. 

137.  The  influence  of  the  mode  of  .fold- 
ing of  the  blade  in  the  bud  on  its  final 
shape  is  well  illustrated  by  the  leaf  of  the 
Tulip  tree  (Liriodendron,  Fig.  66).     The 
end  of  the  lamina  is  seen  to  be  cut  off,  as 
it  were,  or  truncate.     There  are  also  pro- 
jections, or  lobes,  on  either  side.     Figure 
68  shows  how  the  lobes,  and  recesses,  and 
the  truncation  fit  the  space  which  the  very 
young  blade  occupies  between  and  around 
other  parts  of  the  developing  bud.     Fig- 
ure   67   shows   the   blade,    with   its   two 

67.  winter  bud  of    halves  flatly  folded  together,  in  the  win- 

Liriodendron,  ,      , 

ter  bud. 

138.  The  benefit  of  equal  illumination 

for  all  the  leaves  may  well  be  the  cause 


with  some 
of  the  outer 
scales  turned 
back. 


OUT.  OF  HOT.  — 6 


82 


THE  LEAF 


68.  A  young  bud  of  Lirio- 
dendron,  much  en- 
larged, showing  the 
manner  in  which  the 
blade  of  a  young 
leaf  is  shaped  in  its 
growth  by  the  con- 
figuration of  the 
parts  upon  which  it 
lies  folded.  —  LUB- 

BOCK. 


of  many  leaf  shapes.  Leaves  standing  side  by  side  on  the 
same  bough  or  around  the  same  stem  are  thus  shaped 
so  that  they  fit  well  together  with 
little  overshading.  Divided  and  com- 
pound blades  (see  §  177)  seem  to  be 
better  than  entire  forms  in  the  matter 
of  allowing  sunlight  to  filter  through 
to  foliage  on  lower  parts  of  the  stem. 

139.  Perhaps   enough   cases   have 
been  given  to  make  it  clear  that  the 
philosophy    of   leaf    forms   is   to   be 
sought  in  the  circumstances  of  life 
of  the  different  sorts  of  plants. 

140.  Division    of   the    blade:    the 
margin.  —  The  margin  of  the  blade 
may    be    even,    or    entire,    through- 
out.    Oftener  it  is  more  or  less  in- 
dented.     If   slightly  irregular,    and 
the  projections  are  pretty  sharp,  the 

margin  is  toothed,  or  dentate  (Fig.  Ill)  ;  or,  if  the  teeth 
point  forward  like  those  of  a  ripsaw,  the  margin  is  serrate 
(Fig.  110).  If  the  depressions  are  rather  deep  and  sharp, 
like  cuts,  the  margin  is  incised  (Fig.  115).  Large  projec- 
tions, especially  if  somewhat  rounded,  are  termed  lobes. 
All  degrees  and  kinds  of  marginal  irregularity  are  similarly 
designated  by  proper  terms  for  the  ready  description  and 
recognition  of  the  various  species  of  plants :  in  two  or 
three  words  the  botanist  may  describe  any  one  of  the 
almost  endlessly  diversified  shapes  of  leaves  so  as  to  give 
a  definite  idea  of  it. 

141.  Compound  leaves.  —  The  blade  is  often  so  deeply 
divided  that  it  consists  of  quite  separated  parts.     The  blade 
(and  the  leaf)  is  then  compound  (Figs.  59,  124).     Each 
part  often  has  a  stalklet  of  its  own,  and  the  stalklet  (or 
petiolule)  is  often  jointed  with  the  main  leaf  stalk  just  as 
this  is  jointed  with  the  stem. 

142 .  Leaves  with  no  distinction  of  petiole  and  blade.  —  The  leaves 
of   Iris   show   one  form  of  this.      The  flat   but  narrow   leaves   of 


THE  LEAF 


83 


Jonquils,  Daffodils,  and  the  cylindrical  leaf  of  Onions  are  other 
instances.  Needle-shaped  leaves,  like  those  of  the  Pine,  Larch,  and 
Spruce,  are  examples. 

LEAVES   OF  SPECIAL  CONFORMATION  AND  USE 

143.  Leaves   for  storage.  —  A  leaf  may  at  the  same  time  serve 
both  ordinary  and  special  uses.     Thus  in  those  leaves  of  Lilies,  such 
as  the  common  White  Lily,  which  spring  from  the  bulb,  the  upper 
and  green  part  serves  for  foliage  and  elaborates  nourishment,  while 
the  thickened  portion  or  bud  scale  beneath  serves 

for  the  storage  of  this  nourishment.  The  thread- 
shaped  leaf  of  the  Onion  fulfills  the  same  office, 
and  the  nourishing  matter  it  prepares  is  deposited 
in  its  sheathing  base,  forming  one  of  the  concen- 
tric layers  of  the  Onion.  When  these  layers,  so 
thick  and  succulent,  have  given  up  their  store  to 
the  growing  parts  within,  they  are  left  as  thin  and 
dry  husks. 

144.  Leaves  as  bud  scales  have  already  been 
studied. 

145.  Leaves  as  spines  occur  in  several  plants. 
A  familiar  instance  is  that  of  the  common  Bar- 
berry (Fig.  69).     In  almost  any  summer  shoot 
most  of  the  gradations  may  be  seen  between  the 
ordinary  leaves,  with  sharp  bristly  teeth  and  leaves 
which  are  reduced  to  a  branching  spine  or  thorn. 

The  fact  that  the  spines  of  the  Barberry  produce  a  leaf  bud  in  their 
axils  also  proves  them  to  be  leaves. 

146,  Leaves      for      climbing.  —  The 

leaves  of  several  common  climbing  or 
clambering  plants,  one  of  which  has 
been  figured  in  another  place  (page  54), 
are  roughened  on  the  ribs  and  margins 
like  the  stem,  as  an  aid  to  climbing. 
Even  without  roughening,  the  outstand- 
ing leaves  and  side-stems  of  plants  of 
this  general  habit  support  the  shoots 
as  they  weave  their  way  through  the 
thickets  and  latticed  herbage.  It  is  but 
a  step  from  the  mere  resting  of  the  leaf 
ro.  Tendril  leaves  of  on  chance  supports  to  the  habit  of  hook- 

jets-    .  i    i 

ing  °ver  them,  more  or  less  ;  and  but 


69.  The  common 
Barberry. 


Solanum 


84 


THE  LEAF 


another  step  to  winding  about  them  in  the  fashion  of  a 
tendril.     The  complete  adoption  of  the  clasping  habit, 

taken  on  in  this  case 
by  the  petiole,  is  seen 
in  the  Solanum  jas- 
minoides  of  the  gar- 
dens (Fig.  70)  and 
the  common  Clem- 
atis. 

147.  Or  the  ten- 
dril habit  may  orig- 
inate in  the  blade 
itself.  Thus  the  pro- 
longed medium  portion  of  the  blade  in  Crloriosa  (Fig.  71) 
curves  round  the  supporting  object.  This  is  a  simple 
leaf.  Several  compound 
leaves,  as  those  of  the  Pea 
and  Sweet  Pea,  have  the 
extremity  of  the  main 
stalk,  or  rachis,  developed 


71.  Tendril  leaves  of  Gloriosa  superba. 


If 


72.  Tendril  leaves  of  Lathy- 
rus  Aphaca,  the  stipules 
performing  the  duty  of 
foliage. 

into  a  tendril  having  all 
the  qualities  of  the  stem- 
tendrils  before  described. 
The  leaflets  also,  in  these 

cases,  may  be  transformed  73-  Tendril  leaf  of  Cobsea  macrostemma  ; 

st,  main  stem  of  the  plant ;  If,  the 
for  the  Same  purpose.       In  extent  of  a  single  leaf. 


THE  LEAF 


85 


a>  mo^e  °^  attachment  of  the  tendril 
tips  to  a  support;  6,  the  clawed  ex- 
tremity, enlarged. 


Lathyrus  Aphaca  (Fig.  72)  only  the  stipules  remain  to 
perform  the  offices  of  the  blade. 

148.  One  of  the  most 
remarkable  of  tendril 
leaves  is  that  of  the 
Cobcea  figured  herewith 
(Fig.  73).  The  tendril 
portion  branches  several 
times.  Each  branch 
again  divides  and  sub- 
divides. The  final  sub- 
divisions are  clawed 
(Fig.  74). 

Owing  to  the  dichot- 

omous  —  or   two-forked  —  branching,    neighboring    claws 
cooperate  in  catching  slender  objects  coming  into  the  axils 

of  the  dichotomy,  as  the 
jaws  of  a  pair  of  ice  tongs 
act  together  in  holding  the 
block  of  ice.  The  tendril, 
therefore,  catches  with  great 
readiness  upon  anything  it 
may  strike  as  the  leaf  is 
swayed  by  the  breeze.  Yet 
the  leaf  is  far  from  depend- 
ent upon  the  winds  for  mo- 
tion. Like  the  extremity 
of  a  twining  stem,  it  makes 
regular  revolutions.  The 
leaf  from  which  the  figure 
was  drawn  made  complete 
revolutions  in  one  hour  and 
ten  minutes,  the  end  swing- 
ing round  a  circle  about  one 
foot  in  diameter.  The  mo- 
tion is  easy  to  see,  since  the 
average  rate  of  progress  is  about  one-third  the  rate  at 
which  the  end  of  the  second  hand  of  a  watch  travels. 


75.   Coiling  of  the  tendril  after  having 
fastened  to  a  support. 


86 


THE  LEAF 


The  actual  motion  is  often  faster  than  this,  since  the  for- 
ward movement  is  interrupted  by  retracings  of  the  path 
and  by  up  and  down  or  oblique  deviations  from  the 
level  course. 

149.  In  case  a  twig  or  stem  of  another  plant  is  encoun- 
tered, the  tendril  bends  round  it  and  the  clawed  extremities 
catch  in  the  bark  (Fig.  74,  a).     The  several  divisions  of 
the  tendril,  with  their  numerous  hooks,  lay  hold  on  the 
newly  found  support,  and  soon  twist  about  it,  while  the 
rachis  shortens  by  coiling  (Fig.  75),  in  the  manner  char- 
acteristic of  tendrils. 

150.  The  leaves  of  insectivorous  plants.  —  The  habitat 
of  insectivorous  plants  is  chiefly  marshes,  like  peat  bogs. 

Those  that  the  student  will 
be  most  likely  to  meet  are 
the  Sundews  and  Pitcher 
Plants.  The  commonest, 
Sundew  (Drosera  rotundi- 
folici),  is  a  little  plant, 
generally  acaulescent,  with 
its  five  or  six  rounded 
leaves  spread  out  horizon- 
tally in  a  rosette  from  two 
to  four  inches  in  diameter. 
The  leaves  are  thickly  set 
with  hairlike  organs  (Fig. 
76),  each  tipped  with  a 
glistening  drop  of  sticky 
secretion.  To  •  judge  from 
the  number  of  small  insects, 
mainly  gnats  and  flies,  usually  found  sticking  on  the  leaves 
of  the  Sundew,  it  seems  not  unlikely  that  the  plants  exer- 
cise upon  them  some  attraction,  perhaps  through  an  odor, 
perhaps  only  by  the  brilliance  of  the  clear  secretion  drops 
shining  in  the  sun,  and  the  color  of  the  purplish  glands. 

151.  The  gland-tipped  outgrowths  are  tentacles.     The 
marginal  ones  are  the  longest,  and  when  fully  spread  out 
in  all  directions,  double  the  total  diameter  of  the  leaf.     If 


76.  A  leaf  of  Drosera  rotundifolia,  or 
round-leaved  Sundew  (x2). 


THE  LEAF  87 

a  small  fly  touches  the  viscid  globule  at  the  extremity 
of  one  of  these  tentacles,  he  is  at  once  securely  held ;  the 
liquid  being  extraordinarily  sticky,  and  so  tenacious  when 
drawn  out  into  little  strings  that  considerable  motion  may 
be  imparted  to  the  whole  leaf  through  a  single  filament 
before  it  is  broken.  In  its  efforts  to  free  itself,  the  fly  is 
likely  to  strike  neighboring  tentacles  with  its  legs  and 
wings.  All  the  tentacles  touched  begin  almost  at  once  to 
bend  inward,  toward  the  center  of  the  leaf.  The  fly  is,  in 
fact,  finally  deposited  on  the  shorter  tentacles  of  the  blade. 
Then  from  all  sides  the  tentacles  converge  toward  the  cap- 
tured insect,  and  their  glands  pour  upon  it  secretions  of 
digestive  fluid,  which  now  begins  to  flow,  resembling  the 
digestive  secretions  of  the  animal  stomach.  The  soft  parts 
of  the  insect  are  dissolved  and  the  products  of  digestion 
absorbed  by  the  glands.  Subsequently  the  tentacles  re- 
expand,  and  the  secretions  dry  up,  so  that  the  remains  of 
the  insect  may  be  blown  away  or  shaken  off.  The  secre- 
tions appear  again  after  a  time,  in  readiness  for  new  prey. 

152.  Bending  of  the  tentacles  was  distinctly  observed 
by  Darwin   ten   seconds   after   excitation.      The    closing 
together  of  the  tentacles  takes  from  one  to  four  or  five 
hours.     The  tentacles  expand  again  in  from  one  to  seven 
days,  according  to  the  nature  of  the  exciting  object. 

153.  Pitcher  Plants.  —  Pitcher  Plants,  of  the  type  repre- 
sented by  the  genus  Sarracenia,  are  also  low  bog  plants. 
Their  general  habit,  and  the  shape  of  their  leaves  —  the 
upward-curving   tube,    the   wing   on    one   side,  and   the 
rounded,  more  or  less  arching  hood  at  the  apex,  —  are  seen 
in  the  accompanying   illustration   (Fig.   77).      In   some 
species  the  hood  quite  overarches  the  mouth  of  the  pitcher. 
Its  surface  and  that  of  the  throat  of  the  pitcher  are  set 
with  stiff  downward-pointing  bristles.     The  tube  is  habitu- 
ally half  filled  with  water,   in   which  the  fragments  of 
insects,  in  all  stages  of  decomposition,  may  be  found  in 
considerable  quantities.      In  most   species   these  insects 
have  been  lured  by  secretions  of  honey  to  the  rim  of  the 
pitcher  ;  and  then  slipping  on  the  extraordinarily  smooth 


88 


THE  LEAF 


77.   Sarracenia  purpurea,  the  Pitcher  Plant  of 
the  Northern  United  States. 


surface,  their  descent  aided  by  the  direction  of  the  bristly 

hairs,  they  have  fall- 
en helplessly  into  the 
liquid  below.  The 
liquid  exudes  from 
the  tissues  of  the 
leaf  itself  ;  though 
the  spreading  hood 
of  Sarracenia  pur- 
purea  must  catch  a 
certain  amount  of 
rain.  To  what  ex- 
tent the  dissolution 
of  the  captured 
insects  is  promoted 
by  digestive  ele- 
ments produced  by 

^^e   Ditcher    to   what 

extent  by  ordinary 
decay,  is  not  certain.  It  is  held,  however,  that  the 
organic  solutions  are  absorbed  and  used  by  the  plant. 

154.  Insects  are  caught  in  another 
way,  and  more  expertly,  by  the  most 
extraordinary  of  all  the  plants  of  this 
country,  the  Dioncea  or  Venus's  Fly- 
trap, which  grows  in  the  sandy  bogs 
around  Wilmington,  North  Carolina. 
Here  (Fig.  78)  each  leaf  bears  at  its 
summit  an  appendage  which  opens  and 
shuts,  in  shape  something  like  a  steel 
trap,  and  operating  much  like  one. 
For  when  open,  no  sooner  does  a  fly 
alight  on  its  surface,  and  brush  against 
any  one  of  the  two  or  three  bristles  that 
grow  there,  than  the  trap  suddenly 
closes,  capturing  the  intruder.  If  the  fly  escapes,  the 
trap  soon  slowly  opens,  and  is  ready  for  another  cap- 
ture. When  retained,  the  insect  is  after  a  time  moistened 


THE  LEAF   .  89 

by  a  secretion  from  minute  glands  of  the  inner  surface, 
and  is  digested. 

155.  The  Bladderwort,  one  of  the  most  interesting  of  our  car- 
nivorous plants,  should  be  sought  in  still  water  of  ponds  and  large 
pools —  where  it  is  common  —  and  examined  under  the  lens.   Nepenthes, 
the  East  Indian  Pitcher  Plant,  is  not  uncommon  in  greenhouses.     In 
nature  it  grows  as  an  epiphyte  on  trees. 

156.  The  development  of  devices  for  entrapping  animals,  on  the 
part  of  the  carnivorous  plants,  has  the  following  significance.    These 
plants  are  found  in  places  where  nitrogenous  compounds  are  scarce. 
If  their  roots  reach  soil,  it  is  merely  wet  sand  or  mud,  poor  in  com- 
bined nitrogen.     Often   the   plants   are  aquatic  or  epiphytic.     The 
animals  caught  are  rich  in  nitrogenous  food,  and  so  supply  just  that 
nutritive  element  which  could  not  otherwise  be  obtained. 

157.  Duration  of  leaves.  —  The  leaves  of  such  trees  as  the  Elm, 
Maple,  Chestnut,  Linden,  and  so  on,  last  but  a  single  season  and  then 
fall  off.     Their  leaves  are  deciduous;   and  the  trees  themselves  are 
spoken  of  as  deciduous  trees,  meaning  trees  with  deciduous  foliage. 
Evergreen  leaves  last  more  than  one  season  at  least.     Those  of  the 
Pines  and  Firs  persist  for  two  to  five  years,  or  in  some  cases  more. 
In  the  Conifer,  Abies  Pinsapo,  the  age  of  the  leaf  reaches  sixteen  or 
seventeen  years. 

158.  The  fall  of  deciduous  leaves  is  not  caused  by  their  death. 
Even  before  they  begin  to  turn  yellow  in  the  autumn,  the  disarticulation 
is  begun  which,  when  complete,  allows  them  to  drop  away,  leaving  a 
clean  scar.     Before  this  event,  a  large  part  of  the  useful  substances  in 
the  active  tissue  of  the  blade  is  withdrawn  and  saved  to  the  plant. 
The  brilliant  colors  of  autumn  foliage  are  the  signs  that  the  living 
matter  is  being  chemically  changed  preparatory  to  this  withdrawal. 
Frost  and  cold  have  only  an  indirect  effect,  if  any,  in  bringing  about 
the  high  coloration. 

The  Arrangement  of  Leaves 

159.  It  has  come  to  the  student's  notice  in  the  study  of  buds  and 
of  the  stem  that  leaves  are  given  off  from  the  stem  in  somewhat  defi- 
nite fashion ;    at  least  in  such  cases  as  that  of  the  Horse-chestnut, 
where  they  occur  in  pairs,  on  opposite  sides  of  the  stem.     The  regu- 
larity would  not  be  so  apparent  in  the  leafy  branch  of  the  Apple. 
Yet  here,  too,  a  little  attention  shows  a  pretty  definite  system  in  the 
disposition  of  the  leaves.     The  study  of  leaf  arrangement  is  called 
Phyllotaxy. 

160.  The  attachment  of  the  leaf  to  the  stem  is  the  insertion.    Leaves 
are  inserted  in  three  different  modes.     They  are 


90 


THE  LEAF 


Alternate,  that  is  one  after  another;  or  with  only  a  single  leaf  to 
each  node ; 

Opposite,  when  there  is  a  pair  to  each  node,  the  two  leaves  in  this 
case  being  always  on  opposite  sides  of  the  stem ; 

Whorled  or  verticillate,  when  there  are  more  than  two  leaves  on  a 
node,  in  which  case  they  divide  the  circle  equally  between  them,  form- 
ing a  verticel  or  whorl.  When  there  are  three  leaves  in  the  whorl, 
the  leaves  are  one-third  of  the  circumference  apart;  when  four,  one- 
quarter  ;  and  so  on.  So  the  plan  of  opposite  leaves  is  merely  that  of 
whorled  leaves,  with  the  fewest  leaves  to  the  whorl ;  namely,  two. 

161.  Phyllotaxy  of  alternate  leaves.  —  Alternate  leaves  are  distrib- 
uted along  the  stem  in  an  order  which  is  tolerably  uniform  for  each 
species.  The  arrangement  in  all  its  modifications  is  said  to  be  spiral, 
because,  if  we  draw  a  line  from  the  insertion  (i.e.  the  point  of  attach- 
ment) of  one  leaf  to  that  of  the  next,  and  so  on,  this  line  will  wind 
spirally  around  the  stem  as  it  rises,  and  in  the  same  plant  will  commonly 
bear  the  same  number  of  leaves  for  each  turn 
round  the  stem.  That  is,  any  two  successive 
leaves  will  always  be  separated  from  each 
other  lay  an  equal  portion  of  the  circumfer- 
ence of  the  stem.  The  distance  in  height 
between  any  two  leaves  may  vary  greatly, 
even  on  the  same  shoot,  for  that  depends  upon 
the  length  of  the  internodes,  or  spaces  between 
the  leaves;  but  the  distance  as  measured 
around  the  circumference  (the  angular  diver- 
gence, or  angle  formed  by  any  two  successive 
leaves)  is  practically  the  same. 

162.  Two-ranked.  —  The  greatest  possible 
divergence  is,  of  course,  where  the  second  leaf 
stands  on  exactly  the  opposite  side  of  the  stem 
from  the  first,  the  third  on  the  side  opposite 
the  second,  and  therefore  over  the  first,  and 
the   fourth   over    the    second.      This    brings 
all  the  leaves  into  two  ranks,  one  on  one  side 
of  the  stem  and  one  on    the  other,  and  is 
therefore  called  the  two-ranked  arrangement. 
Next  is  the 

163.  Three-ranked  arrangement, — that  of 
all  Sedges,  and  of  White  Hellebore.      Here 

the  second  leaf  is  placed  one-third  of  the  way  round  the  stem,  the 
third  leaf  two-thirds  of  the  way  round,  the  fourth  leaf  accordingly 
directly  over  the  first,  the  fifth  over  the  second,  and  so  on.  That  is, 
three  leaves  occur  in  each  turn  round  the  stem,  and  they  are  separated 
from  each  other  by  one-third  of  the  circumference  (Fig.  79). 


79.  Three-ranked  ar- 
rangement, shown 
in  a  piece  of  the 
stalk  of  a  Sedge, 
with  the  leaves  cut 
off  above  their 
bases ;  the  leaves 
are  numbered  in 
order,  from  1  to  6. 


THE  LEAF 


91 


0-" 


5-ranked  arrangement :  80, 
shoot  with  its  leaves  5-ranked, 
the  sixth  leaf  over  the  first,  as 
in  the  Apple  Tree ;  81,  diagram 
of  this  arrangement. 


164.  Five-ranked  is  the  next  in  series,  and  the  most  common.     It 
is  seen  in  the  Apple  (Fig.  80),  Cherry,  Poplar,  and  the  greater  number 
of  trees  and  shrubs.     In  this  case 

the  line  traced  from  leaf  to  leaf 
will  pass  twice  round  the  stem 
before  it  reaches  a  leaf  situated 
directly  over  any  below.  Here 
the  sixth  leaf  is  over  the  first; 
the  leaves  stand  in  five  perpen- 
dicular ranks,  with  equal  angular 
distance  from  each  other ;  and 
this  distance  between  any  two 
successive  leaves  is  just  two- 
fifths  of  the  circumference  of  the 
stem. 

165.  The  above  arrangements 

of  spirally  placed  leaves  are  the  80-81. 
most  common.  A  three-eighths 
or  five-thirteenths  divergence  is 
not  uncommon.  It  will  be  noted 
that  the  precise  arrangement  may 
be  indicated  by  a  fraction,  thus :  the  two-ranked  by  i,  the  three-ranked 
by  $,  the  five-ranked  by  f,  and  so  on  with 
the  f,  T5^,  and  other  arrangements,  the  whole 
fraction  indicating  the  angular  divergence  of 
the  leaves,  while  the  denominator  shows  the 
number  of  vertical  ranks.  It  will  be  seen 
that,  beginning  with  f,  any  one  of  the  frac- 
tions may  be  derived  by  adding  the  numera- 
tors of  the  two  preceding  fractions  for  the 
following  numerator,  and  in  like  manner 
adding  the  two  preceding  denominators  for 
the  new  denominator. 

166.    Phyllotaxy  of  opposite  and  whorled 
leaves.  —  This  is  simple  and  comparatively 
uniform.     The  leaves  of  each  pair  or  whorl 
are  placed  over  the  intervals  between  those 
\.*)Y  of  the  preceding,   and  therefore  under  the 

^~Jj  intervals  of  the  pair  or  whorl  next  above. 

fj  The  whorls  or  pairs  alternate  or  cross  each 

82.  Opposite  leaves  of  Eu-  other,  usually  at  right  angles,  that  is,  they 
onymus,  or  Spindle  decussate  (Fig.  82).  Opposite  leaves,  that 
Tree,  showing  the  jgj  whorls  of  two  leaves  only,  are  far  com- 

crossi'gTachoth'er     moner  thau  whorls  of  three  or  four  or  more 
at  right  angles.  members. 


92 


THE  LEAF 


TERMS  USED  IN  THE  DESCRIPTION  OF  LEAVES 

[Inserted  for  reference  use  by  classes  making  the  determination  of 
plants  a  part  of  their  course.] 

167.  Forms  of  leaves  as  to  general  outline.  —  It  is  necessary  to 
give  names  to  the  principal  shapes,  and  to  define  them  rather  precisely, 
since  they  afford  easy  marks  for  distinguishing  species.  The  same 
terms  are  used  for  all  other  flattened  parts  as  well,  such  as  petals ;  so 
that  they  make  up  a  great  part  of  the  descriptive  language  of  Botany. 
Beginning  with  the  narrower  and  proceeding  to  the  broadest  forms,  a 
leaf  is  said  to  be 

Linear  (Fig.  83),  when  narrow,  several  times  longer  than  wide,  and 
of  the  same  breadth  throughout. 

Lanceolate,  or  Lance-shaped,  when  conspicuously  longer  than  wide, 
and  tapering  upwards  (Fig.  84),  or  both  upwards  and  downwards. 

OUong  (Fig.  85),  when  nearly  twice  or  thrice  as  long  as  broad  and 
of  uniform  breadth. 

Elliptical  (Fig.  86),  when  similar  to  oblong  but  with  continuously 
rounding  sides. 

Oval,  when  broadly  elliptical,  or  elliptical  with  the  breadth  con- 
siderably more  than  half  the  length. 

Ovate  (Fig.  87),  when  the  outline  is  like  a  section  of  a  hen's  egg 
lengthwise,  the  broader  end  toward  the  stern. 


85 


86 


87 


88 


83-88.  A  series  of  shapes  of  feathered-veined  leaves :  83,  linear ;  84, 
lanceolate ;  85,  oblong ;  86,  elliptical ;  87,  ovate ;  88,  cordate. 


Orbicular,  or  Rotund  (Fig.  97),  circular  in  outline,  or  nearly  so. 

A  leaf  which  tapers  toward  the  base  instead  of  toward  the  apex 
may  be 

Oblanceolate  (Fig.  89),  when  of  the  lance-shaped  form,  only  more 
tapering  toward  the  base  than  in  the  opposite  direction. 

Spatulate  (Fig.  90),  when  more  rounded  abeve,  but  tapering  thence 
to  a  narrow  base,  like  an  old-fashioned  spatula. 

Obovate  (Fig.  91),  when  inversely  ovate,  that  is,  ovate  with  the  nar- 
rower end  toward  the  stem. 

Cuneate,  or  Cuneiform,  that  is,  Wedge-shaped  (Fig.  92),  broad  above 
and  tapering  by  nearly  straight  lines  to  an  acute  angle  at  the  base. 


THE  LEAF 


93 


168.    As  to  the  base,  its  shape  characterizes  several  forms,  such  as 

Cordate,  or  Heart-shaped  (Figs.  88,  94),  when  a  leaf  of  an  ovate 
form,  or  something  like  it,  has  the  outline  of  its  rounded  base  turned 
in  (forming  a  notch  or  sinus),  where  the 
stalk  is  attached. 

Reniform,  or  Kidney-shaped  (Fig.  96), 
like  the  last,  only  rounder  and  broader 
than  long. 

Auriculate,  or  Eared,  having  a  pair  of 
small  and  blunt  projections,  or  ears,  at 
the  base,  as  in  one  species  of  Magnolia 
(Fig.  99). 

Sagittate,  or  Arrow-shaped,  where  such 
ears  are  acute  and  turned  downwards, 
while  the  main  body  of  the  blade  tapers  upwards  to  a  point,  as  in 
the  common  Sagittaria  or  Arrowhead,  and  in  the  Arrowleaved  Poly- 
gon um  (Fig.  98). 

93 


90  91  92 

89-92.  Feather- veined  leaves : 
89,  oblanceolate ;  90, 
spatulate;  91,  obovate; 
92,  wedge-shaped. 


96  9T 

93-97.  Various  forms  of  radiate- 
veined  leaves :  93,  94,  cor- 
date; 95,  96,  reniform; 
97,  peltate. 


99 


100 


98-100.  Feather-veined  leaves:  98, 
sagittate;  99,  auriculate;  100, 
halberd-shaped  or  hastate. 


Hastate,  or  Halberd-shaped,  when  such  lobes  at  the  base  point  out- 
wards, giving  the  shape  of  the  halberd  of  the  olden  time,  as  in  another 
Polygonum  (Fig.  100). 

Peltate,  or  Shield-shaped  (Fig.  97),  is  the  name  applied  to  a  curious 
modification  of  the  leaf,  commonly  of  a  rounded  form,  where  the  foot- 
stalk is  attached  to  the  lower  surface  instead  of  the  margin,  and  there- 
fore is  naturally  likened  to  a  shield  borne  by  the  outstretched  arm. 
The  common  Watershield,  the  Nelumbo,  and  the  White  Water  Lily, 
and  also  the  Mandrake,  exhibit  this  sort  of  leaf. 

169.  As  to  the  apex,  the  following  terms  express  the  principal 
variations :  — 

A  cuminate,  Pointed,  or  Taper-pointed,  when  the  summit  is  more  or 
less  prolonged  into  a  narrowed  or  tapering  point;  as  in  Fig.  101. 


94  THE  LEAF 

Acute,  ending  in  an  acute  angle  or  not  prolonged  point;  Fig.  102. 

Obtuse,  with  a  blunt  or  rounded  apex  ;  as  in  Fig.  103,  etc. 

Truncate,  with  the  end  as  if  cut  off  square  ;  as  in  Fig.  1(M. 

Refuse,  with  rounded  summit  slightly  indented,  forming  a  very 
shallow  notch,  as  in  Fig.  105. 

Emarginate,  or  Notched,  indented  at  the  end  more  decidedly  ;  as  in 
Fig.  106. 

Obcordate,  that  is,  inversely  heart-shaped,  where  an  obovate  leaf  is 
more  deeply  notched  at  the  end  (Fig.  107),  as  in  White  Clover  and 
Wood-sorrel  ;  so  as  to  resemble  a  cordate  leaf  inverted. 


104      105        106      107     108   109 


101-109.  Forms  of  the  apex  of  leaves:  101,  acuminate;  102,  acute;  103,  ob- 
tuse; 104,  truncate  ;  105,  retuse;  106,  emarginate  ;  107,  obcordate  ;  108, 
cuspidate,  109,  mucronate. 

Cuspidate,  tipped  with  a  sharp  and  rigid  point  ;  as  in  Fig.  108. 

Mucronate,  abruptly  tipped  with  a  small  and  short  point,  like  a 
mere  projection  of  the  midrib;  as  in  Fig.  109. 

Aristate,  Awn-pointed,  and  Bristle-pointed,  are  terms  used  when  this 
mucronate  point  is  extended  into  a  longer  bristle-form  or  slender 
appendage. 

The  first  six  of  these  terms  can  be  applied  to  the  lower  as  well  as 
to  the  upper  end  of  a  leaf  or  other  organ.  The  others  belong  to  the 
apex  only. 

170.  As  to  degree  and  nature  of  division,  there  is  first  of  all  the 
difference  between 

Simple  leaves,  those  in  which  the  blade  is  of  one  piece,  however 
much  it  may  be  cut  up,  and 

Compound  leaves,  those  in  which  the  blade  consists  of  two  or  more 
separate  pieces,  upon  a  common  leafstalk  or  support.  Yet  between 
these  two  kinds  every  intermediate  gradation  is  to  be  met  with. 

171.  As  to  particular  outlines  of  simple  leaves  (or  the  parts  of 
compound  leaves),  they  are 

Entire,  when  their  general  outline  is  completely  filled  out,  so  that 
the  margin  is  an  even  line,  without  teeth  or  notches. 

Serrate,  or  Saiv-toothed,  when  the  margin  is  cut  into  sharp  teeth,  like 
those  of  a  ripsaw,  that  is,  pointing  forwards;  as  in  Fig.  110. 

Dentate,  or  Toothed,  when  such  teeth  point  outwards,  instead  of 
forwards;  as  in  Fig.  111. 

Crenate,  or  Scalloped,  when  the  teeth  are  broad  and  rounded  ;  as  in 
Fig.  112. 


THE  LEAF 


95 


110 


114    115 


Repand,  Undulate,  or  Wavy,  when  the  margin  of  the  leaf  forms  a 
wavy  line,  bending  slightly  inwards  and  outwards  in  succession;  as 
in  Fig.  113. 

Sinuate,  when  the  margin  is 
more  strongly  sinuous  or  turned 
inwards  and  outwards ;  as  in 
Fig.  114. 

Incised,  Cut,  or  Jagged,  when 
the  margin  is  cut  into  sharp, 
deep,  and  irregular  teeth  or  in- 
cisions; as  in  Fig.  115. 

Lobed,     when     deeply     cut. 
Then  the  pieces  are  in  a  gen-    110-115.  Kinds  of  margin  of  leaves :  110, 
eral  way  called    LOBES.      The  serrate;    111,  dentate?   112,  ere- 

i          .  .,       ,  i        •     ,    •  a  nate;  113,  repaud;  114.  sinuate; 

number  of  the  lobes  is  briefly  115>  incjsed. 

expressed  by  the   phrases   two- 

lobed,  three-lobcd,  five-lobed,  many-lobed,  etc.,  as  the  case  may  be. 

When  the  depth  and  character  of  the  lobiug  needs  to  be  more  par- 
ticularly specified,  the  following  terms  are  employed,  viz. :  — 

Lobed,  in  a  special  sense,  when  the  incisions  do  not  extend  deeper 
than  about  halfway  between  the  margin  and  the  center  of  the  blade, 

if  so   far,  and   are 

117  more  or  less  round- 

ed;  as  in  the 
leaves  of  the  Post 
Oak,  Fig.  116,  and 
the  Hepatica,  Fig. 
120. 

Cleft,  when  the 
incisions  extend 
halfway  down  or 
more,  and  especially 
when  they  are  sharp; 
as  in  Figs.  117,  121. 
And  the  phrases 
two-cleft,  or,  in  the 
Latin  form,  bifid, 
three-cleft  or  trifid, 
four-cleft  or  quadri- 
fiL  five-cleft  or  quin- 
quefid,  etc.,  or  many- 
cleft,  in  the  Latin  form,  multifid, — express  the  number  of  the  segments, 
or  portions. 

Parted,  when  the  incisions  are  still  deeper,  but  yet  do  not  quite 
reach  to  the  midrib  or  the  base  of  the  blade ;  as  in  Figs.  118, 122.  And 


116-123.  Margins  of  deeply  cut  leaves :  116,  pinnately 
lobed;  117,  pinnately  cleft;  118,  pinnately 
parted ;  119,  pinnately  divided ;  120,  pal- 
mately three-lobed ;  121,  palmately  three- 
cleft;  122,  palmately  three-parted;  123, 
palmately  three-divided,  or  trisected. 


96  THE  LEAF 

the  terms  two-parted,  three-parted,  etc.,  express  the  number  of  such 
divisions. 

Divided,  when  the  incisions  extend  quite  to  the  midrib,  as  in  the 
lower  part  of  Fig.  119,  or  to  the  leafstalk,  as  in  Fig.  123;  which  really 
makes  the  leaf  compound. 

172.  The  mode  of  lobing  or  division  corresponds  to  that  of  the 
veiuiug,  whether  pinnately  veined  or  palmately  veined.     In  the  former 
the  notches  or  incisions,  or  sinuses,  corning  between  the  principal  veins 
or  ribs  are  directed  toward  the  midrib :  in  the  latter  they  are  directed 
toward  the  apex  of  the  petiole ;  as  the  figures  show. 

173.  So  degree  and  mode  of  division  may  be  tersely  expressed  in 
brief  phrases.     Thus,  in  the  four  upper  figures  of  pinnately  veined 
leaves,  the  first  is  said  to  be  pinnately  lobed  (in  the  special  sense),  the 
second  pinnately  cleft  (or  pinnatifid  in  Latin  form),  the  third  pinnately 
parted,  the  fourth  pinnately  divided. 

174.  Correspondingly  in  the  lower  row,  of  palmately  veined  leaves, 
the  first  is  palmately  lobed,  the  second  palmately  cleft,  the  third  palmately 
parted,  the  fourth  palmately  divided.     Or,  in  other  language  of  the 
same  meaning  (but  now  less  commonly  employed),  they  are  said  to  be 
digitately  lobed,  cleft,  parted,  or  divided. 

175.  The  number  of   the  divisions  or  lobes   may  come   into  the 
phrase.    Thus  in  the  four  last  named  figures  the  leaves  are  respectively 
palmately   three-lobed,  three-cleft    (or   trifid),  three-parted,  three-divided. 
And  so  for  higher  numbers,  as  Jive-lobed,  Jive-cleft,  etc.,  up  to  many-lobed, 
many-cleft,  or  multifid,  etc.    The  same  mode  of  expression  may  be  used 
for  pinnately  lobed  leaves,  as  pinnately  seven-lobed,  -cleft,  -parted,  etc. 

176.  The  divisions,  lobes,  etc.,  may  themselves  be  entire  (without 
teeth  or  notches),  or  serrate,  or  otherwise  toothed  or  incised ;  or  lobed, 
cleft,  parted,  etc. :   in  the  latter  cases  making  twice  pinnatifid,  twice 
palmately  or  pinnately  lobed,  parted  or  divided  leaves,  etc.     From  these 
illustrations  one  will  perceive  how  the  botanist,  in  two  or  three  words, 
may  describe  any  one  of  the  almost  endlessly  diversified  shapes  of 
leaves,  so  as  to  give  a  clear  and  definite  idea  of  it. 

177.  Compound  leaves.  —  A  compound  leaf  is  one  which  has  its 
blade  in  entirely  separate  parts,  each  usually  with  a  stalklet  of  its  own ; 
and  the  stalklet  is  often  jointed  (or  articulated)  with  the  main  leaf- 
stalk, just  as  this  is  jointed  with  the  stem.  When  this  is  the  case,  there 
is  no  doubt  that  the  leaf  is  compound.     But  when  the  pieces  have  no 
stalklets,  and  are  not  jointed  with  the  main  leafstalk,  it  may  be  con- 
sidered either  as  a  divided  simple  leaf,  or  a  compound  leaf  according 
to  the  circumstances.     This  is  a  matter  of  names  where  all  intermedi- 
ate forms  may  be  expected. 

178.  While  the  pieces  or  projecting  parts  of  a  simple  leaf  blade  are 
called  lobes,  or  in  deeply  cut  leaves,  etc.,  segments  or  divisions,  the  sepa- 
rate pieces  or  blades  of  a  compound  leaf  are  called  LEAFLETS. 


THE  LEAF 


97 


124^126.  Pinnate  leaves :  the  first  with  an  odd  leaflet 
(odd-pinnate) ;  the  second  with  a  tendril  in 
place  of  uppermost  leaflets ;  the  third  abruptly 
pinnate,  or  of  even  pairs. 


179.  Compound  leaves  are  of  two  principal  kinds,  namely,  the 
pinnate  and  the  palmate;  answering  to  the  two  modes  of  veining  in 
reticulated   leaves,  and  to  the  two  sorts  of  lobed  or  divided  leaves 
(Figs.  116,  120). 

180.  Pinnate  leaves  are  those  in  which  the  leaflets  are  arranged  on 
the  sides  of  a  main 

leafstalk  ;  as  in 
Figs.  124-126.  They 
answer  to  (he  feather- 
veined  (i.e.  pinnately- 
veinecT)  simple  leaf; 
as  will  be  seen  at 
once  on  comparing 
the  forms.  The  leaf- 
lets of  the  former 
answer  to  the  lobes 
or  divisions  of  the 
latter;  and  the  con- 
tinuation of  the  peti- 
ole, along  which  the 
leaflets  are  arranged, 
that  is,  the  leaf  rachis  answers  to  the  midrib  of  the  simple  leaf. 

181.  Three  sorts  of  pinnate  leaves  are  here  given.     Fig.  124  is  pin- 
nate with  an  odd  or  end  lea/let,  as  in  the  Common  Locust  and  the  Ash. 
Fig.  125  is  pinnate  with  a  tendril  at  the  end,  in  place  of  the  odd  leaflet, 
as  in  the  Vetches  and  the  Pea.     Fig.  126  is  evenly  or  abruptly  pinnate, 
as  in  the  Honey  Locust. 

182.  Palmate  (also  named  digitate}  leaves  are  those  in  which  the 
leaflets  are  all  borne  on  the  tip  of  the  leafstalk,  as  in  the  Lupine, 

the  common  Clover,  the  Virginia  Creeper, 
the  Horse-chestnut  and  Buckeye  (Fig.  127). 
They  evidently  answer  to  the  radiate  veined 
or  palmately  veined  simple  leaf. 

183.  Either  sort  of  compound  leaf  may 
have  any  number  of  leaflets;  yet  palmate 
leaves  cannot  well  have  a  great  many,  since 
they  are  all  crowded  together  on  the  end 
of  the  main  leafstalk.  Some  Lupines  have 
nine  or  eleven ;  the  Horse-chestnut  has 
seven,  the  Sweet  Buckeye  more  commonly 
five,  the  Clover  three.  A  pinnate  leaf  often 
has  only  seven  or  five  leaflets,  or  only  three, 
as  in  the  Beans  of  the  genus  Phaseolus,  etc. ;  in  some  rarer  cases  only 
two;  in  the  Orange  and  Lemon  and  also  in  the  common  Barberry 
there  is  only  one.  The  joint  at  the  place  where  the  leaflet  is  united 

OUT.   OP  HOT. 7 


127.  Palmate  (or  digitate) 
leaf  of  five  leaflets 
of  the  Sweet  Buck- 
eye. 


THE  LEAF 


with  the  petiole  distinguishes  this  last  case  from  a  simple  leaf.     In 
other  species  of  these  genera  the  lateral  leaflets  also  are  present. 

184.  The  leaflets  of  a  compound  leaf  may  be  either  entire  (as  iu 
Figs.  124-126),  or  serrate,  or  lobed,  cleft,  parted,  etc. ;  in  fact,  may  pre- 
sent all  the  variations  of  simple  leaves, 

and  the  same  terms  equally  apply  to 
them. 

185.  When  the  division  is  carried 
so  far  as  to  separate  what  would  be 
one  leaflet  into  two,  three,  or  several, 
the  leaf  becomes  doubly  or  twice  com- 
pound, either  pinnately  or  palmately,  as 
the  case  may  be.     For  example,  while 
the    clustered    leaves    of    the   Honey 
Locust  are  simply  pinnate,  that  is,  once 
pinnate,  those  on  new  shoots  are  bipin- 
nate,  or  twice  pinnate,  as  in  Fig.  128. 
AVhen  these  leaflets  are  again  divided 
in    the   same  way,  the   leaf  becomes 
\hrice  pinnate,  or  tripinnate,  as  in  many 
Acacias.    The  first  divisions  are  called 
pinnce;   the  others,  pinnules;  and  the 
last,     or     little     blades    themselves, 
leaflets. 

186.  So  the  palmate  leaf,  if  again  compounded  in  the  same  way. 
becomes  twice  palmate,  or,  as  we  say  when  the  divisions  are  in  threes, 

twice  ternate  (in  Latin  form  biternate*)',  if  a 
third  time  compounded,  thrice  ternate  or  triter- 
nate.  But  if  the  division  goes  still  further, 
or  if  the  degree  is  variable,  we  simply  say 
that  the  leaf  is  decompound;  either  palmately 
or  pinnately  decompound,  as  the  case  may  be. 
Thus,  Fig.  129  represents  a  four  times  ter- 
nately  compound  (in  other  words  a  ternatelij 
decompound}  leaf  of  a  common  Meadow  Rue. 

187.    When    the    botanist,    in    describing 

129.  Teruately     decom-   leaves,  wishes  to  express  the  number  of  the 
leaflets,  he  may  use  terms  like  these  :  — 

Unifoliolate,  for  a  compound  leaf  of  a  single 
leaflet;    from  the  Latin  unum,  one,  and  foliolum,  leaflet. 

Bifoliolate,  of  two  leaflets,  from  the  Latin  bis,  twice,  and  foliolum, 
leaflet. 

Trifoliolate  (or  ternate),  of  three  leaflets,  as  the  Clover,  and  so  on. 
Palmately  bifoliolate,    trifoliolate,    quadrifoliolate,  plurifoliolate    (of 
several  leaflets),  etc. :  or  else 


128.  A  twice-pinnate  (abruptly) 
leaf  of  the  Honey  Locust. 


pound      leaf 

Meadow  Rue. 


of 


LABOE4TORY  STUDIES   OF  THE  FLOWER  99 

Pinnately  bi-,  trt-,  quadri-,  or  pluri-foliolate  (that  is,  of  two,  three, 
four,  or  several  leaflets),  as  the  case  may  be :  these  are  terse  ways  of 
denoting  in  single  phrases  both  the  number  of  leaflets  and  the  kind 
of  compounding. 


XI.    LABORATORY  STUDIES  OP  THE  FLOWER 

The  object  of  the  flower  is  the  bearing  of  seed  for  the  reproduction 
of  the  plant.  It  is  best  to  examine  at  once  the  seed  rudiments  with 
the  parts  in  which  they  are  borne,  and  those  equally  important  prod- 
ucts, the  pollen  grains,  which  act  upon  the  seed  rudiments  to  make 
them  capable  of  growth  into  seed,  as  well  as  the  organs  which  bear 
the  pollen.  After  that  the  less  important,  though  more  showy,  parts 
of  the  flower  are  to  be  studied. 

EXERCISE  XXIX.     THE  RUDIMENTS  OF  THE  SEEDS 

Look  the  flower  over  as  well  as  possible,  without  pulling  it  to 
pieces,  to  see  what  the  various  parts  are  like.  Note  in  a  general  way, 
without  drawing,  the  number,  arrangement,  and  varied  shapes  of  the 
parts. 

Remove  the  members  at  one  side  in  order  to  get  at  the  central 
organ,  the  pistil.  Cut  this  off  at  the  end  gradually  until  white,  seed- 
like  bodies  —  the  ovules  —  are  brought  to  view. 

Cut  down  the  sides  wherever  necessary  in  order  to  split  off  the 
outer  walls,  so  as  to  leave  the  ovules  undisturbed  and  exposed  to  view 
in  their  natural  positions.  "* 

Examine  with  the  lens,  noting:  — 

(1)  the  arrangement ; 

(2)  the  number  of  rows  hi  each  compartment; 

(3)  the  attachment  of  the  ovules; 

(4)  the  number  of  compartments. 

The  hollow  portion  of  the  pistil  is  the  ovary;  its  compartments 
are  termed  cells.  The  middle  part  of  the  ovary,  where  the  walls  of 
the  cells  meet,  is  the  axis.  The  partitions  between  the  cells  are  the 
dissepiments.  The  surface  where  the  ovules  are  attached  in  a  cell  is 
the  placenta ;  if  there  are  several  cells  there  are  several  placentae.  The 
manner  in  which  the  ovules  are  placed,  as  concerns  attachment,  is  the 
placentation.  If  they  are  attached  to  the  axis  the  placentation  is 
axile ;  if  to  the  walls  of  the  cell,  it  is  parietal. 

Add  to  your  notes  a  few  words  describing  the  pistil  in  hand  as  to 
the  number  of  cells  and  th'e  placentation. 

Taking  up  a  fresh  flower,  for  the  moment,  note  how  the  pistil  ends 
above.  The  somewhat  enlarged  end  with  granular  or  loose  tissue  on 
the  surface  is  the  stigma.  Below  this  the  pistil  is  often  narrowed,  so 


100          LABORATORY  STUDIES   OF  THE  FLOWER 

that  the  stigma  is  raised  on  a  more  or  less  slender  column,  the  style. 
When  seated  on  the  ovary  the  stigma  is  sessile.  Draw  the  pistil  and 
label  the  parts. 

Draw  the  ovary  with  walls  removed,  side  view,  to  show  the  ovules 
in  position  (x  4-6);  end  view,  to  show  placentation  and  number  of 
cells  of  ovary  (x  3-5). 

Examine  the  ovules,  removed,  with  the  highest  power  of  the  dis- 
secting microscope,  or,  perhaps,  with  a  compound  microscope.  Draw  a 
side  view,  including  the  little  stalk  of  attachment  to  the  placenta. 

EXERCISE  XXX.     THE  POLLEN 

Examine  the  organs  standing  next  to  the  pistil  —  the  stamens. 
Find  one  opened  and  shedding  its  yellow,  mealy  contents,  the  pollen ; 
and  one  not  yet  opened. 

f.f  a  high  power  is  available  examine  and  draw  the  individual 
grains. 

Cut  a  thin  cross  section  o?.  the  unopened  stamen  to  show  the 
cavities  in  which  the  pollen  is  produced  —  the  pollen  sacs. 

Note  where  the  pollen  sacs  open,  or  dehisce. 

Draw  a  stamen  (x  2-3).  The  stalk  is  the  filament.  The  pollen- 
bearing  terminal  portion  is  the  anther.  The  continuation  of  the  fila- 
ment, or  the  part  that  connects  the  pollen  sacs,  is  the  connective.  Label 
all  parts.  Draw  anther,  side  view,  to  show  dehiscence  (  x  3-5)  ;  cross 
section  of  anther  showing  the  pollen  sacs  (  x  5-10). 

The  really  essential  parts  of  the  flower  have  now  been  seen.  The 
ovules,  acted  upon  by  the  pollen,  give  rise  to  new  plants.  Many 
flowers  have  no  other  parts  than  pistils  or  stamens ;  that  is,  no  pro- 
tecting envelopes  such  as  the  brightly  colored  leaves  of  the  flower 
which  i>  now  being  studied.  These  leaves  are  of  great  service  in  pro- 
moting the  transfer  of  pollen  from  flower  to  flower  and  in  protecting 
the  pistil  and  stamens  while  they  are  maturing.  But  they  take  only 
an  indirect,  not  a  strictly  necessary,  part,  in  reproduction. 

EXERCISE  XXXI.     THE  FLORAL  ENVELOPES 

Are  there  two  sets  of  the  floral  leaves  ?  Do  they  differ  in  any 
respect  except  in  position  ?  Draw  one  member  of  each  set  if  there  is 
a  difference. 

Examine  one  of  the  floral  leaves  under  the  lens  with  transmitted 
light,  shading  meanwhile  from  direct  light,  to  discover  any  venation. 
If  any  is  found  indicate  this  on  the  drawing. 

The  leaflike  organs  together  are  the  perianth.  When  in  two  dis- 
tinct sets,  the  outer  set  is  the  calyx,  the  members  being  the  sepals ;  the 
inner  is  the  corolla,  made  up  of  petals. 


LABORATORY  STUDIES   OF  THE  FLOWER          101 


EXERCISE  XXXII. 


THE   PARTS  OF   THE   FLOWER   IN   RELATION 
TO  ONE  ANOTHER 


Cut  a  new  flower  neatly  in  halves  lengthwise. 

Draw  the  half  flower  as  seen  from  the  cut  side,  to  show :  — 

(1)  the  shape  of  the  pistil; 

(2)  the  relative  positions  and  heights  of  the  other  parts. 

The  summit  of  the  flower  stem,  generally  somewhat  enlarged,  from 
which  the  organs  spring,  is  the  receptacle. 

Looking  down  upon  or  into  the  flower,  endwise,  make  out  the  rela- 
tive position  of  the  sepals,  petals,  stamens,  and  cells  of  the  ovary. 

When  these  have  been  made  out  definitely,  make  a  diagram  of  the 
flower  as  seen  from  above,  in  the  following  manner :  — 
1st.  Represent  the  ovary  in  cross  section. 

2d.    In  a  circle  —  if  so  found  in  the  flower  —  around  the  ovary, 
roughly  indicate  the  cross  sections  of  the  anthers,  properly 
placed  as  regards  direction  from  the  ovary  cells. 
3d.    Represent  petals  by  arcs  of  a 
circle,  properly  placed ;  the 
arcs   may   be   thickened   a 
little  at  the  middle  to  repre- 
sent midribs  of  the  petals. 
4th.    Outside  these  draw  similar 
figures   for, the   sepals,   in 
the     proper     places     with 
respect  to  the  other  parts. 
The    diagram    thus    constructed 
shows  the  ground  plan  of  the  flower. 
The  annexed  figure  shows  the  method 
of  constructing  such  diagrams. 

In  case  any  two  parts  of  the 
flower  are  grown  together,  as  two 
petals,  or  a  petal  and  a  sepal,  as 
sometimes  happens,  this  fact  may 
easily  be  indicated  in  the  diagram 
by  drawing  a  dotted  line  between 
the  conjoined  members. 


129  a.  Flower  and  floral  diagram 
of  Trillium. 


EXERCISE   XXXIII.      THE   ARRANGEMENT   OF   THE   FLOWERS    ON 
THE  STEM  OR  STEMS  :   OR  INFLORESCENCE 

When  flowers  come  in  clusters  they  are  found  in  one  of  two  differ- 
ent types  of  inflorescence.  Either  a  flower,  early  produced,  ends  the 
main  stem  of  the  cluster,  so  that  no  further  growth  of  the  cluster  in 
the  line  of  the  axis  is  possible ;  in  this  case  new  flowers  are  produced 
only  on  side  branches,  and  these  side  flowers  are  younger  than  that 


102          LABORATORY  STUDIES   OF  THE  FLOWER 

on  the  central  axis  of  inflorescence;  or  the  cluster  goes  on  growing  in 
the  main  axis  and  putting  out  new  flowers  for  a  time,  —  so  that  the 
lower  flowers  are  older,  the  upper  ones  younger.  The  first  type  is 
called  determinate,  or  cymose  ;  the  second,  indeterminate,  or  racemose. 

Determine  the  type  of  inflorescence  in  the  material  furnished. 
•  Draw  a  diagram  of  the  arrangement  of  the  flowers,  letting  lines  rep- 
resent the  stems,  branches,  and  individual  flower  stalks  (or  pedicels), 
and  putting  at  the  ends  dots  for  the  flowers,  larger  for  the  older,  and 
smaller  for  the  younger,  flowers. 

Turn  to  the  figures  of  the  different  sorts  of  cymose  and  racemose 
inflorescences  (page  140  and  following),  and  select  the  proper  term 
for  the  material  in  hand. 

EXERCISE  XXXIV.     THE  FLOWER  OF  A  CONIFEROUS  PLANT 

1.  The  Staminate  Flower 

Cut  a  longitudinal  section.  Note  the  positions  of  the  stamens. 
Draw  the  outline  of  the  whole  flower  (or  cone)  and  the  central  axis, 
and  indicate  the  position  and  outline  of  two  or  three  stamens. 

Detach  one  stamen.  Note  its  general  form,  and  the  number  of 
pollen  sacs.  Do  the  sacs  lie  on  the  under  or  the  upper  side  of  the 
stamen?  Find  out  about  the  place  where  the  sacs  open  for  the  emis- 
sion of  pollen.  Draw  one  stamen,  so  as  to  show  the  pollen  sacs 
opened. 

Are  there  any  scales  or  other  structures  answering  to  the  perianth 
of  an  angiospermous  flower? 

Note  the  size  and  number  of  the  pollen  grains  and  examine  with  the 
compound  microscope  if  possible. 

2.  The  Pistillate  Flower 

Before  cutting  into  the  flower  (or  cone),  note  the  arrangement  of 
the  scales. 

Note  also  the  outstanding  edges  of  the  scales ;  this  feature  is  related 
to  the  method  of  pollination. 

Draw  a  simple  outline  of  the  cone,  and  then  indicate  diagrammati- 
cally  the  arrangement  of  the  scales ;  that  is,  draw  simple  continuous 
lines  for  the  boundaries  of  the  rows  of  scales.  Can  you  see  rows  in 
more  than  one  direction  ?  If  so,  draw  the  diagram  accordingly. 

Break  the  cone  across.  Separate  one  of  the  scales.  On  careful 
examination  it  will  be  seen  that  the  scale  is  double,  so  that  there 
seem  to  be  two  scales  with  a  common  base.  The  under  one  is  the 
smaller.  The  upper  one  is  the  placental  scale,  or  ovuliferous  scale. 

Examine  the  upper  surface  of  the  placental  scale  for  two  promi- 
nences near  the  base.  Each  has  a  few  short  filaments  projecting 
toward  the  axis  of  the  cone.  The  prominences  are  the  ovules.  The 


THE  FLOWER 


103 


filaments  serve  to  catch  the  pollen  when  it  has  fallen  upon  the  cone 
and  down  between  the  scales  to  the  ovules. 

Draw  upper  and  under  views,  to  show  the  two  scales  and  the  ovules. 

FURTHER  WORK  ON  THE  FLOWER 

The  study  of  the  flower,  as  far  as  many  of  the  details  are  concerned, 
depends  so  much  on  the  available  material  that  specific  directions  had 
best  be  left  to  the  teacher. 

For  suggestions  as  to  systematic  study  of  flowering  plants,  see  the 
Appendix. 


XII.    THE  FLOWER 
GENERAL   MORPHOLOGY  OF   THE  FLOWER 

188.  The  flower  is  destined  to  produce  seed ;  the  seed, 
to  bring  forth  a  plant  of  the  next  generation.  At  the 
center  of  the  flower  bud,  in  their  proper  cavities  the 
beginnings  of  the  seed  rudiments  are  distinguishable  long 
before  the  flower  is  ready  to  open.  If,  after  the  bud 


130.  A  flower  of  the  Cherry  Tree  cut 
open  to  show  the  single  ovule 
in  its  receptacle,  the  ovary. 


finally    Ullfolds     and     the     several     131-  The  ovary  of  Mandrake 
.,  ,  opened  at  one  side  to 

envelopes  separate,  the  receptacle  show   the    numer0us 

seen    within    is    CUt    Open,    One    Or  ovules,  each  contain- 

ing the  starting  point 

two,  often  several,  and  not  uncom-  of  a  new  plant, 

monly  very  many,  rounded  bodies 

are  discovered,  —  white,  shining,  and  translucent,  spring- 
ing in  definite  and  orderly  arrangement  from  the  walls 
or  the  central  axis.  These  are  the  ovules  (Figs.  130,  131). 
To  these  small  vesicles  the  life  of  the  species  of  plants 
which  bear  them  is  for  a  time  intrusted.  Each  one  car- 


104 


THE  FLOWER 


ries  within  it  an  inheritance  of  the  racial  characteristics: 
the  forms  of  the  leaves,  the  colors  of  the  flower,  the  height 
and  character  of  the  stem,  even  the  movements  of  the 
parent  plant  are  passed  down  through  the  ovule  (with  the 
aid,  as  will  shortly  be  seen,  of  the  pollen)  to  the  plant 
which  is  to  spring  from  the  ovule. 

189.  The  ovule-bearing  organ  is  the  pistil  (Fig.  132). 
Three  parts  are  usually  distinguishable  :  the  hollow  lower 
portion  is  the  ovary ;  the  column  sur- 
mounting this  is  the  style;  and  at  the 
tip  of  the  style  —  sometimes  on  its 
side  —  a  part  of  the  surface  without 
epidermis  and  moist  or  even  sticky, 
is  termed  the  stigma.  The  style  may 
be  lacking ;  the  stigma  is  then  sessile 
on  the  ovary  (Fig.  131). 

190.  The  flower  commonly  contains 
but  one  pistil.  Such  flowers  as  those 
of  the  Pea  and  Bean  illustrate  the 
simplest  case  of  all,  when  the  pistil  is 
solitary  and  has  but  one  cavity  with 
ovules  borne  on  but  one  v  side  -of  it.  In  the  Buttercup 
(Fig.  133)  there  are  many  pistils,  each  simple,  with  a 
single  cavity,  containing  but  a 
single  ovule.  In  the  majority 
of  plants,  however,  the  two  or 
more  original  pistils  grow  up 
from  a  very  early  stage  in  their 
development  united  throughout 
the  greater  part  of  their  length. 
Compound  pistils  are  thus 

formed.  The  several  combined  pistils  are  then  termed 
carpels. 

191.  The  portion  of  the  ovary  to  which  the  ovules  are 
attached  is  the  placenta,  and  the  manner  in  which  the 
ovules  are  distributed  on  the  interior  surfaces  of  the. ovary 
is  the  placentation.  When  the  ovules  are  numerous,,  the 
placenta  is  apt  to  be  a  well-developed  cushion  or  projection 


132.  Pistil  of  Wild  Ge- 
ranium ;  ov,  ova- 
ry ;  stl,  style ; 
stg,  stigma. 


133.  Flower  of  the  Buttercup. 


THE  FLOWER 


105 


of  some  sort  (see  Fig.  138). 
when  no  special  outgx  jwth 
is  to  be  seen, 


But  the  name  applies  even 


134.  The  several  distinct  pistils  of  a 
single  flower.  One  cut  across, 
and  one  cut  lengthwise,  to  show 
the  placentation. 


192.  Types    of    ovary    and 
placentation. — When    the   pis- 
tils are  separate  and  the  ovaries, 
therefore,  one-celled,  the  typical 
arrangement  of   the   ovules  in 
each  ovary  is  in  a  double  verti- 
cal row  on  the  side  nearest  the 
center  of  the  flower  (Fig.  134). 
A  solitary  ovule   may  be  sus- 
pended  from    the    top    of   the 
cell,  or   spring  from   the  side 

toward  the  flower  axis,  or  rise  from  the  bottom. 

193.  When  the  pistil  is  compounded  of  several  carpels,  various 
arrangements  of  the  parts  are  possible.     The  common  one  is  that 

194.  With  two  or  more  cells 
and  axile  placentation  (Figs.  135- 
137).  —  Such  a  pistil  is*just  what 
would  be  formed  if  simple  pis- 
tils, like  those  of  the  Larkspur, 
pressed  together  in  the  center 
of  the  flower,  were  to  cohere  by 
their  contiguous  faces.  In  such 
a  case  the  placentae  are  naturally 
axile,  or  all  brought  together  in 
the  axis  or  center.  The  ovary 
has  as  many  internal  partitions, 
or  dissepiments,  as  there  are  car- 
pels in  the  composition.  When 
such  pistils  ripen  into  pods 
they  often  separate  along  these 
lines  into  their  elementary  car- 
pels. 

195.  One-celled,  with  parietal  placentae  (Figs.  138,  139).  — In  this 
not  uncommon  case  it  is  conceived  that  the  several  original  carpellary 
cavities  are  thrown  into  one  as  the  organ  grows.  The  ovules  now 
spring  from  the  lines  of  junction  of  the  different  carpels.  A  placenta 
belongs  here  half  to  one  carpel,  half  to  another.  At  each  placenta  a 
double  row  of  ovules  is  apt  to  be  found ;  but  the  two  rows  originate 
from  distinct  carpels.  The  number  of  carpels  is  still  to  be  told  from 
the  number  of  placentae.  The  placentation  is  here  termed  parietal. 


135  136  .137 

135-137.  Pistils:  135,  a  Saxifrage,  the 
carpels  or  simple  pistils  united 
below,  free  above;  13(5,  common 
St.  Johnswort,  the  styles  of  the 
carpels  distinct ;  137,  another  St. 
Johnswort,  the  carpels  united 
throughout. 


106 


THE  FLOWER 


196.    One-celled,   with    free    central    placenta.  —  The    free    central 
placenta  of  the  Pink  (compare  Fig.  140)        y  have  come  about  by  the 
dissepiments    having    been    suppressed    in    growth. 
Indeed,  traces  of  the  original  partitions  are  often  to 
be    detected.      On    the    other 
hand,  it  is  equally  supposable 


138.  Placentation 
of  Parnas- 
sia. 


r 

Placentation 
of  Drosera 
filiformis. 


140.  Pistil  of  Spergularia  rubm, 
one  of  the  Pink  family,  with 
free  central  placentation. 


that  in  the  Primrose  (Fig.  160)  the  free  central  placenta  has  been 
derived  from  parietal  placentation  by  the  united  carpels  bearing  ovules 
only  at  the  base.  Now,  however,  the  placenta  arises  directly  from  the 
end  of  the  floral  axis,  not  from  the  carpels. 

197.    To  the  great  majority  of  flowers  with  which  one  meets,  one 
or  another  of  the  above  types  will  apply.     These  types  exhibit  most 

clearly  the  structural  principles  of  the 
pistil.  Occasionally,  some  different 
mode  of  disposing  the  ovules  or  of 
separating  the  ovary  into  chambers 
will  be  discovered. 

198.  Pistils    of    the    Gymno- 
sperms.  —  These  are  so  distinct 
and  the  group  of   plants  which 
produce    them    is    so   important 
that   they  need   a   separate   de- 
scription. 

199.  The  fertile  flowers  of  the 
Pine1   and    other   trees    of    the 
same  group  appear  in  early  spring 
as    small    richly    colored    cones 
(Fig.  141).     The  scales  are  soft, 
and   though    not   very  thin   are 

1  What  is  here  designated  a  single  female  flower  is  also  spoken  of  as 
an  inflorescence. 


141.  The  flower  of  a  Gymno- 
sperm.  At  the  right  a 
single  carpellary  scale 
bearing  two  ovules. 


THE   FLOWER  107 

rather  leaflike.  Each  fertile  scale  bears  on  its  upper  sur- 
face near  the  base  a  pair  of  ovules.  In  such  flowers  the 
pistils,  therefore,  are  not  closed,  and  the  seed  throughout 
its  history  is  naked,  i.e.  exposed.  Accordingly,  the  cone- 
bearing  trees  and  their  relatives  are  designated  as  GYMNO- 
SPEBMS  (naked  seeded). 

200.  The    corresponding   term    for   plants  with  closed 
ovaries  is  ANGIOSPERMS.     Angiospermous  flowers  will  be 
meant  in  this  chapter  unless  otherwise  stated. 

201.  The  stigma  has  been  described  as  a  definite  portion 
of  the  surface  of  the  style,  or,  when  the  style  is  lacking, 
of  the  ovary.     When  the  tip  of  the  style  is  enlarged  in 
a  knob,  or  branched,  or  finely  dissected  in  a  plume  (Fig. 
166),  it  is  convenient  to  speak  of  the  whole  organ  —  and 
not  merely  the  surface  —  as  the  stigma. 

Under  the  lens  and  even  to  the  naked  eye  the  stigmatic 
surface  is  distinguished  by  a  granular  texture  and  often 
by  a  viscid  secretion,  designed  to  secure  the  pollen  grains 
which  fall  upon  it  or  are  brought  to  it. 

202.  For  the  ovules  are   not   the  sole  conceptacles  of 
racial  life  as  it  is  passed  onward  from  one  generation  to 
the   next.       Other  and  simpler  bodies   produced  in  the 
flower  are  equally  freighted  with  inheritance,  namely,  the 
individual  pollen  grains,  emitted  in  multitudes  as  yellow 
dust  by  the   floral   or- 
gans   standing    around 

the     pistil     or    pistils. 
Each    "  grain  "    viewed 

0  .  142.   Various  forms  of    pollen,   magnified, 

through  the  microscope  illustrating  the  manner  in  which  the 

is  86611  to  be  a  Spherical  wal1  is  sculptured  in  different  species 

body.  (Fig.    166) -in 

many  cases,  however,  elongated  or  otherwise  modified  — 
of  the  simplest  description  as  regards  structure.  It  con- 
sists of  a  minute  portion  of  living  substance  of  jellylike 
consistency,  surrounded  by  a  tough  elastic  coat  or  wall. 
As  will  shortly  be  seen,  this  body  is  capable  of  growth, 
and  plays  an  equally  important  part  with  the  ovule  in  the 
reproduction  of  plants. 


108 


THE  FLOWER 


203. 


p 


The  pollen-bearing  organ  is  the  stamen  (Fig.  143) 
Its  parts  are  the  stalk,  called 
the  filament,  and  the  anther, 
containing  the  pollen  in  pollen 
sacs.  In  the  young  condition 
of  the  stamen  four  longitudi- 
nal pollen  sacs  are  found. 
The  whole  mass  of  tissue 
filling  these  sacs  is  finally  con- 
verted to  pollen.  At  matu- 
rity, if  not  before,  the  wall 
between  the  two  cavities  on 
143.  a,  a  stamen ;  p,  pollen  sac:  c,  the  same  side  of  the  anther 

connective;    f,  tilameut;  b,  IT  i          • 

a  stamen  with  the  anther    commonly  disappears,  leaving 
cut  through  at  the  time  of    a  single  pollen  sac  in   either 

maturity.  ,  •  , ,,        , ,  ~, 

halt-anther.     The  middle  part 

or  axis  of  the  anther  between  the  two  pouches  thus  formed 
is  the  connective. 

204.  The  pollen  sacs  open  for  the  liberation  of  the  pollen 
usually  by  a  slit  along  the  groove  running  down  each  side 
of  the  anther ;  in  Pyrola  and  other  members  of  the  Heath 
family,  by  terminal  pores  (Fig.  144) ; 

and  in  the  Barberry  by  uplifting 
valves  (Fig.  145).  And  other  modes 
of  dehiscence  occur,  suited  to  the 
various  means  by  which  the  pollen 
is  to  reach  its  destination. 

205.  The    number    of    stamens  is 
often  large,  as  in  the  wild  Rose,  the 

Buttercup,   the    Magnolia,    and   the    144, 145.  stamens :  144,  of 

,         T*?  ?  .        ,,  Pyrola,   the    auther 

Water  Lily.  In  a  tew  species  there 
is  but  one.  Generally  speaking,  the 
number  is  small,  not  more  than  ten ; 
and,  when  small,  usually  definite  for 
each  species.  For  example,  most  grasses  have  three  sta- 
mens, most  Mints  four,  the  Violets  five,  and  the  true 
Lilies  commonly  six.  Each  pollen  sac  produces  a  vast 
number  of  pollen  grains.  And  when  the  flowers  borne 


144 


opening  by  terminal 
pores ;  145,  ol  Bar- 
berry, the  anther 
opening  by  uplifting 
valves. 


THE  FLO  WEE 


109 


by  the  plant,  or  the  stamens  in  the  individual  flowers,  are 
very   numerous,    the    pollen   may    be   exceedingly 
abundant. 

206.  In  a  few  families  the  stamens  are  regularly 
united,  either  by  the  anthers  —  as  in  the  Composite, 
of  which  the  Daisy  is  an  example;  or  by  the  fila- 
ments,  as    in   the   Mallows  and 

the  LeguminosoB  (e.g.  the  Sweet- 
pea,  Bean,  etc.,  Figs.  146-148). 

207.  The  pistils  collectively  are 
known   as    the   gynoecium ;    the 
stamens  as  the  andrcecium.     It 
is  well  to  hold  clearly  in  mind 
that  these  two  groups  of  organs,      u6 

though   often    concealed    Or   ren-  146-148.  United  stamens:  146,  of  a 

,        j     .                                                        .  plant  of  the  Pulse  family ; 

dered   inconspicuous  by  the  vi-  147,  in  the  Mallow  family; 

cinity  of   highly   colored    floral  148>  stamens  united   by 

anthers  in  the  Composite 

envelopes,    are    essentially    the  family, 

flower.      That  is  to  say,  pistils 

and  stamens  perform  the  essential  function  of  the  flower ; 

and  the  floral  leaves 
act    a   subordinate 
part.       Not     very 
rarely  flowers  con- 
sist   of    pistils    or 
stamens      alone. 
This  is  practically 
the     case     in     the 
Willows.     The  familiar 
catkins  are  of  two  kinds. 
The   more    showy   ones 
are  made  up  of  numer- 
ous flowers,  each   com- 
prising stamens,  usually 
two,  with  a  scale  at  the 
base.     In  catkins  of  the 
other  sort  each   minute 
flower   is   composed   of 


149 


150 


152 


151 


149-152.  Flowers  of  a  Willow:  149,  staminate 
catkin  ;  150,  one  of  the  flowers ;  151 ,  pis- 
tillate catkin ;  152,  a  pistillate  flower. 


110 


THE  FLOWER 


a  single  pistil  with  the  basal  scale  (Figs.  149-152).  The 
seed-bearing  flowers  of  the  Pine  and  other  Coniferce,  as 
already  described,  contain  only  pistils;  their  pollen- 
bearing  flowers,  only  stamens.  When  a  flower  lacks 
both  gynoecium  and  andrcecium,  it  either  becomes  merely 
tributary  to  other,  fertile  flowers  —  as  in  the  case  of  the 
marginal  florets  in  the  heads  of  the  Sunflower — or  it 
lacks  altogether  the  essential  character  of  a  flower  proper, 
as  regards  purpose,  either  directly  or  indirectly  ;  as  in  the 
double  Rose  and  other  flowers  transformed  by  cultivation. 

208.  The  floral  leaves  together  are  called  the  perianth, 
meaning  about  the  flower  —  a  term  not  far  from  appropriate 
if  what  has  just  been  said  is  allowed.     Commonly,  two 
distinct  sets  of  these  leaves  are  present  :  the  inner  called 
petals,  together  forming   the    corolla;    the  outer  termed 
sepals,  composing  the  calyx. 

209.  The   number   of   sepals   and  petals  in  particular 
species  is  generally  constant.    In  a  majority  of  the  Dicotyle- 
dons' the  sepals  are  five,  and  the  petals  five,  though  four  is 
a.  common  number  ;   in  Monocotyledons  the  members  of 

the  perianth  are  prevailingly  in 
threes.  As  the  stamens  are  apt 
to  be  as  many  or  twice  as  many 
as  the  petals  or  sepals,  a  numerical 
plan  is  often  prominent  in  the 
parts  of  the  flower.  We  say  that 
the  flowers  of  the  Dicotyledons 
are  often  on  the  plan  of  five,  those 
of  the  Monocotyledons  on  the  plan 
of  three. 

210.  Forms  of  the  corolla.  —  As 
an  example  of  the  regular  corolla 
—  i.e.  with  petals  all  alike  —  the 
flowers  of  any  of  the  Rose  family 
may  be  recalled  ;  but  the  Colum- 
bine (Fig.  153)  as  well,  since  all  the  petals  are  spurred, 
presents  a  regular  corolla.  In  the  Violet  (Fig.  154),  on 
the  contrary,  only  one  petal  is  spurred,  and  the  petals 


153.  Flower  of  the  Colum- 
bine. 


THE  FLOWER 


111 


154.  Flower  of  the  Violet ; 
below,  the  parts  of 
the  perianth  sepa- 
rated. 


are  of  unequal  size  :  such  corollas,  and  all  in  which  the 

petals  are  not  entirely  uniform,  are 

irregular. 

211.  A  second  important  respect  in 
which  corollas  differ  is  in  the  sepa- 
ration or  union  of  the  petals.  The 
trumpet-shaped  corolla  of  the  Morn- 
ing Glory  (Fig.  155)  furnishes  an 
extreme  instance  of  union,  where  the 
original  petals  are 
not  easily  distin- 
guishable. Fre- 
quently the  limb, 
or  border,  is  so 
lobed  that  the 

number  of  component  parts  is  evident. 
Another  familiar  form  is  the  two- 
lipped,  labiate,  corolla  (Fig.  169). 

212.  In  case  the  petals  remain  quite 
separate,  the  corolla  is  said  to  be  poly- 
petalous  ;  but  if  they  grow  up  united  when  the  floral 
organs  are  in  process  of  formation,  the  corolla  becomes 
gamop&talous.  When  the  petals  are  all  wanting,  the 
flower  is  apetalous. 

213.  The  calyx  presents  features  very  similar  to  the 
corolla  as  regards  union  of  sepals  and  other  modifications. 
It  is  usually  inferior  to  the  corolla  in  size  and  coloration, 
since  its  service  is  chiefly  to  protect  the  bud,  of  which  it 
forms  the  coat.     But  in  numerous  plants  the  calyx  shares 
with  the  corolla  in  another  duty. 

214.  Functions  of  the  perianth.  —  The  role  of  the  perianth 
in  the  natural  history  of  the  flower  is  chiefly  twofold  : 
(1)  it  protects  the  developing  organs  within  while  the  bud 
is  coming  to  maturity  ;  and  (2)  at  the  time  of  blooming 
it  aids  in  the  proper  distribution  of  the  pollen.     Without 
anticipating  the  subject  of  fertilization,  it  may  be  said  that 
it  is  of  advantage  to  plants  to  secure  the  dusting  of  the 
stigma  of  each  flower  by  the  pollen  of  some  other  flower  of 


155.  Calyx  and  corolla 
of  Morning  Glory. 


112 


THE  FLOWER 


the  same  kind,  and  that  this  is  most  commonly  accom- 
plished by  the  aid  of  insects.  The  various  forms  of  the 
perianth  are,  as  a  rule,  very  definitely  related  to  the  work 
of  attracting  the  attention  of  insects,  or  of  receiving  and 
supporting  them  when  they  alight,  or  of  guiding  them  to 
the  "honey"  or  nectar  secreted  by  special  glands  at  the 
base  of  the  flower.  In  view  of  such  offices  the  labiate 
corolla  of  the  Mints,  the  tubular  or  funnelform  corolla  of 
the  Morning  Glory,  the  spurred  (nectariferous)  petals  of 
the  Columbine,  and  the  irregular  flower  of  the  Violet,  are 
readily  understood.  This  subject  will  be  treated  more  fully 
under  The  Ecology  of  the  Flower. 

215.  The  receptacle  of  the  flower  is  that  part  which  be- 
longs to  the   stem.       It  is  commonly  short,    and   some- 
what  enlarged   or   knoblike.      Flowers 
with    very  numerous   pistils    generally 
have  the  receptacle  enlarged  so  as  to 
give  them  room ;   it  sometimes  becomes 
broad   and    flat,    as    in    the    Flowering 
Raspberry ;       sometimes 
elongated,     as     in     the 
Blackberry    (Fig.    256), 

the  Magnolia,  etc.  It  is  the  receptacle  in 
the  Strawberry  (Fig.  156),  much  enlarged 
and  pulpy  when  ripe,  which  forms  the  eata- 
ble part  of  the  fruit,  and  bears  the  small 
seedlike  pistils  on  its  surface.  In  the  Rose 
(Fig.  157),  instead  of  being  convex  or 
conical,  the  receptacle  is  deeply  concave, 
or  urn-shaped.  Indeed,  a  Rose  hip  may  be  likened  to 
a  strawberry  turned  inside  out. 

216.  In  Nelumbo,  of  the  Water  Lily  family,  the  singu- 
lar and  greatly  enlarged  receptacle  is  shaped  like  a  top, 
and  bears  the  small  pistils  immersed  in  separate  cavities  of 
its  flat  upper  surface  (Fig.  158). 

217.  Arrangement  of  the  parts  of  the  flower.  —  This  is 
most  easity  studied    in   those  flowers,  in  which  all  parts 
are    present  —  calyx,    corolla,    stamens,    and    pistils ; 


156.   Section    through 
a  Strawberry. 


157.  Longitudinal 
section  of  a 
Rose. 


Ill 


THE  FLOWER 


113 


158.  The  top-shaped  recep- 
tacle of  Nelumbo, 
the  Water  Chinque- 
pin,  ripening  into  a 
float  for  the  dissemi- 
nation of  the  seeds. 


which  all  the  organs  of  each  kind  are  separate  from  one 

another ;  and  each  set  comprises  a 

small  number,  as  three  or  five.     In 

such  a  case l  it  is  the  rule  to  find 

the  organs  in  whorls,2  and  the  whorls 

arranged  so  that  the  organs  of  one 

whorl   stand   above   the    spaces    of 

the  whorl  below,  just  as  is  the  case 

with  whorled  foliage  leaves.     The 

petals  thus  stand   over  the  spaces 

between   the   sepals,  the   first   row 

of     stamens     alternates    with    the 

petals,  the  second  row  of  stamens 

(if  present)  with  the  first,  and  the  pistils  alternate  with 

the  stamens.     When  the  various  members  of  the  flower 

are  more  numerous  and  the  receptacle   somewhat  elon- 
gated, as  in  the  Magnolia,  the  parts  are  spirally  placed. 

In   short,   the   organs   of   the    flower   are   arranged   like 

leaves. 

218.   Morphology  of  the  floral  parts.  —  Sepals  and  petals 

are  evident  leaves,  as  they  are  commonly  and  properly 

called.  There  are  numerous 
cases  where  green  forms,  func- 
tioning as  foliage,  pass  over 
by  easy  gradations  to  the 
white  or  bright-colored  forms 
subserving  the  purposes  of 
the  flower.  In  shape,  in  fun- 
damental structure  (in  pos- 
sessing veins,  etc.),  and  in 

159.  Transition   from  green  outer  x 

floral  leaves  (sepals),  through    arrangement  on  the  axis,  the 

petals,  to  stamens,  in  Water  tg    ()f     the    perianth    show 

Lily ;  indicating  the  unity  of     r 

nature  of  sepals,  petals,  and     the      morphology     OI      leaves. 

stamens-  Stamens  and  pistils,  also,  agree 

with  leaves  in  the  order  of  insertion  on  the  axis,  as  well 


1  Sometimes  called  a  pattern  flower. 

2  A  whorl  is  a  circular  group  of  several  organs  standing  at  the  same 
level  on  the  axis. 

OUT.  OF  BOX.  — 8 


114  THE  FLOWER 

as  iii  possessing  what  answer  to  the  veins  or  ribs  of  leaves, 
—  fibrous  elements  coming  out  from  the  flower  stem. 
Occasionally  stamens  and  pistils  are  found  which  have 
failed  to  develop  in  their  proper  character.  They  then 
take  the  shape  of  foliage  leaves,  more  or  less  exactly. 
The  conclusion  is  inevitable,  from  all  these  considerations, 
that  the  essential  organs  of  the  flower,  as  well  as  the  floral 
envelopes,  are  morphologically  leaves.1 

219.  The  carpels,  in  this  conception,  become  leaves  rolled  inward, 
bearing  on  the  inrolled  edges  rows  of   ovules.     When  the  pistil   is 
simple  (of  one  carpel  or  leaf),  a  seam,  the  ventral  suture,  marks  the 
closing  together  of  the  ovuliferous  leaf  on  the  side  toward  the  center 
of  the  flower ;  while  a  ridge  up  and  down  the  opposite  side  of  the  pis- 
til evidently  stands  for  a  midrib. 

220.  Departures  from  a  simple  floral  plan.  —  If  one  were  to  examine 
the  first  score  of  different  flowers  that  he  should  meet  on  going  into 
the  field,  he  would  probably  find  among  them  few  or  none  that  display 
the  regularity,  simplicity,  and  completeness  spoken  of  in  §  217.     The 
fundamental  plan  —  that  is,  the  order  and  mode  of  growth,  num- 
ber of  parts,  etc. — would   be  found  in  many  cases  to  be  obscured 
by  a  variety  of  adaptations  to  the  special  functions  of  the  flower. 
Some   of    the   commonest    modifications   to   be   discovered   are  the 
following :  — 

221.  Absence  of  some  of  the  organs.2 —  Occasionally  the  gradual  dis- 
appearance of  some  of  the  organs  may  be  directly  noted,  as  in  stamens 
lacking  the  anther,  or  reduced  to  a  mere  ridge  or  rudiment ;  or  in  the 
reduction  of  one  whorl  of  the  perianth  to  an  inconspicuous  ring.     In 
many  of  the  trees  and  shrubs  the  perianth  will  be  found  to  consist  of 
only  the  calyx  (e.g.  in  the  Elm),  or  it  may  even  be  wanting  (e.g.  in  the 
Buttonwood).     And  two  cases  have  already  been  mentioned  (the  Wil- 
low and  the  Pine)  where  each  flower  contains  but  one  kind  of  essen- 
tial organ. 

222.  Union  of  like  parts,  or  coalescence,  of  which  examples  have 
been  given  above. 

1  This  is  not  to  be  construed  to  mean  that  what  were  once   merely 
foliage  leaves  have  in  the  course  of  time  been  modified  so  as  to  become 
carpels,  stamens,  etc.     All  that  is  to  be  inferred  here  is  that  both  foliage 
leaves  and  floral  organs  have  a  common  morphological  nature,  as  foliar 
appendages  of  the  stem. 

2  It  is  possible  to  suppose  in  some  cases  that  the  fewness  of  parts,  or 
the  absence  of  certain  organs,  has  come  about,  not  by  reduction  from 
more  highly  organized  forms,  but  by  inheritance  from  ancestry  charac- 
terized by  simple  flowers  from  the  first. 


THE  FLO  WEE 


115 


223.  Union  of  unlike  parts,  or  adnation.  —  Frequently  the  stamens 
seem  to  grow  from  the  corolla,  because  the  filaments  have  grown 
to  the  petals  (Figs.  160,  161).  Again,  in  the  flower  of  Cuphea,  for 
example,  calyx,  corolla,  and  stamens  adhere  in  a  cup  around  the  pistil, 


160.   Flower  of  a  Primrose  laid  open; 
co,  corolla ;  ca,  calyx. 


161.  Flower  of  Cuphea  laid  open ; 
ct,  calyx  tube ;  pt,  petals. 


in  such  a  manner  that  both  stamens  and  petals  seem  to  be  inserted  on 
the  margin  of  the  calyx  tube  (Fig.  161).  Finally,  in  the  Purslane 
(Fig.  162)  all  the  different  members  are  united,  with  the  ovary  in  the 
center.  The  ovary  is  in  such  cases  said  to  be  inferior.  When  free 
from  the  organs,  it  is  superior  (Fig.  160).  The  adherence  of  unlike 
members  is  termed  adnation.  In  the  Purslane,  for  example,  the  calyx 
is  said  to  be  adnate  to  the  ovary. 

Coalescence  and  adnation  come  about  in  the  following  manner. 
The  rudiments  of  the  carpels,  stamens,  petals,  and  sepals  appear  at 
first  as  minute  elevations  on  the  young  receptacle.  As  these  increase 
the  surface  of  the  receptacle  between  them  may  be  involved  in  the 
growth.  Thus,  if  the  tissue  between 
the  nascent  petals  is  affected,  a  cir- 
cular ridge  arises,  upon  the  edge  of 
which  the  position  of  the  original 
petal  rudiments  is  indicated  by  prom- 
inences. The  ridge,  or  ring,  grows  up 
into  a  longer  or  shorter  tube  (the 
corolla  tube),  the  original  prominences 
becoming  lobes  or  divisions.  By  a 

similar  process,  in  the  Primrose  (Fig.  160)  the  rudiments  of  the 
stamens  become  united  to  the  corolla  ring  at  an  early  stage.  In 
the  Purslane  (Fig.  162)  a  single  ring  arising  from  the  receptacle, 
and  bearing  all  the  floral  organs  on  its  summit,  comes  to  form  the. 
so-called  "calyx  tube.'* 


162.  Flower  of  the  Purslane. 


116  THE  FLO  WEE 

PROCESSES  LEADING  TO  THE  FORMATION  OF  SEED 

224.  The  student  is  already  aware  that  the  pollen  is 
destined  to  reach  the  stigmatic  surface  of  the  pistil ;  and 
he  probably  also  understands  in  a  general  way  that  the 
result  of  the  pollination  of  a  flower  is  the  production  of 
seed;    that  if  pollination  fails  to  be  brought  about,  the 
ovules  of  the  unpollinated  pistil  do  not  develop  into  fertile 
seed.     The  history  of  the  pollen  from  its  deposition  on 
the  stigma  (pollination)  onward  and  the  resulting  effect 
on  the  ovule  (fertilization)  are  now  to  be  followed. 

225.  The  pollen  grain   has  been  briefly  described  as  a 
simple  vesicle  filled  with  living  matter,  capable  of  growth. 
The  wall  is  relatively  strong,  though  thin  and  transparent, 
and  often  beset  with  projections.     The  living  substance 
within,  termed  protoplasm,  is   more  or   less   jellylike  in 

consistency  and  clearness, 
but  is  far  from  being  a 
simple  mass  of  jelly.  The 
protoplasmic  body  is  in  fact 
very  definitely  and  highly 
organized,  with  permanent 
parts  or  organs  performing 
definite  functions  in  har- 
n  mony  with  one  another. 

163.  A  pollen  grain  highly  magnified.     These     members     may     be 
it  contains  two  nuclei  (n,  ri)     dimly  made  out  in  the  living 

at  the  stage  here  represented.  . 

protoplasm  with  the  com- 
pound microscope.  But  when  killed  and  stained  with 
proper  dyes,  the  structure  stands  out  with  distinctness  and 
its  great  complication  is  then  seen.  A  constant  com- 
ponent is  a  rounded  central  body  of  especially  dense  proto- 
plasm, known  as  the  nucleus  (Fig.  163).  In  the  earlier 
stages  of  the  pollen  grain  there  is  but  one  nucleus.  The 
pollen  grain  is  then  an  excellent  example  of  the  typical 
vegetable  cell. 

226.  Cellular  structure  of  plants.  —  Every  plant  is  made 
of  minute  members,  or  cells,  essentially  similar  to  the 


THE  FLO  WEE 


117 


pollen  grain  in  internal  constitution,  though  of  course 
not  as  to  form  and  external  appearance.  The  cells  of 
vegetable  tissue 
take  on  various 
shapes.  Generally 
their  duration  as 
living  elements  is 
limited.  The  walls 
become  thickened 
and  hardened  and 
remain,  after  the 
death  of  the  cells, 
as  components  of 
the  plant's  frame- 
work (e.g.  the  fibers 
of  wood).  The 
simplest  plants 
among  the  crypto- 
gams consist  of  but 
a  single  cell. 

227.  The    pollen 
grain    a    plant.  — 
In  truth  the  pollen 
grain  itself  behaves 
like  a  simple  plant. 
For  it  absorbs  water 
and      nutriment 
from      the      pistil 
upon   which    it    is 
deposited,  and  uses 
these   materials   in 
growth. 

228.  Growth    is 
manifested  in  two 
ways  :    ( 1 )  in  the 
formation    of    new 


164.  Fertilization  of  the  ovule.  The  pollen  tubes 
traverse  the  loose  tissue  of  the  stigma  and 
style,  finally  emerging  in  the  cavity  of  the 
ovary.  In  the  figure  a  tube  is  represented 
as  applying  itself  to  the  micropyle  of  an 
ovule.  This  ovule  is  seen  in  section,  and 
shows  at  the  micropylar  end  the  embryo- 
sac  with  several  nuclei,  one  of  which  takes 
part  in  the  formation  of  the  embryo. 


nuclei  in  the  proto- 
plasm ;  and  (2)  in  the  extension  of  the  wall  in  a  tube 


118  THE  FLOWER 

(Fig.  164).  The  tube  penetrates  the  tissue  of  the  stigma 
and  style,  and  at  length  reaches  the  cavity  of  the  ovary, 
through  which  it  descends  until  one  of  the  ovules  is 
reached.  Penetrating  the  ovule  at  a  certain  spot,  the 
tube  comes  in  contact  with  the  large  cell,  termed  embryo 
sac,  in  which  the  embryo  is  to  be  formed  (Fig.  164). 

Before  this  time  the  original  pollen  nucleus  has  given 
rise,  by  division,  to  several  nuclei.  One  of  these  nuclei, 
which  has  followed  the  tube  in  its  descent,  now  passes 
over  into  the  embryo  sac  and  fuses  with  one  of  the  sev- 
eral nuclei  to  be  found  there.  From  the  united  body  so 
formed  the  new  plant  takes  its  start.  New  cells  begin 
to  appear  in  the  embryo  sac  and  the  embryo  gradually 
assumes  form.  At  the  same  time  the  whole  ovule,  and 
in  fact  the  entire  ovary,  begins  courses  of  development 
resulting  in  seed  and  fruit  respectively. 

229.  While  every  step  of  this  process — which  can  be 
followed  only  by  aid  of  the  microscope  and  numerous  dis- 
sections—  may  not  be  entirely  clear  to  the  beginner,  the 
brief  account  here  given  should  serve  to  fix  in  mind  the  fact 
that  the  pollen  and  the  ovule  play  very  definite  and  neces- 
sary parts  in  the  life  of  plants ;   and  the  conception  gained 
of  the  method  and  results  of  fertilization,  even  if  some- 
what incomplete,  will  give  the  flower  and  its  varied  forms 
an  added  meaning. 

ECOLOGY  OF  THE  FLOWER 

230.  Self-fertilization  and  cross-fertilization. — Self -fer- 
tilization is  the  action  of  a  flower's  pollen  on  its  own  ovules; 
cross-fertilization,  on  the  ovules  of  some  other  flower,  of  the 
same  species. 

231.  A  limited  number  of  plants  bear  in  addition  to  the 
ordinary  flowers  certain  specialized  flowers  which  are  fer- 
tilized by  their  own  pollen  alone.     The  Violet  is  one  of 
these.     The  vernal  flowers  are  cross-fertilized.     Later  on 
another  set,  of  a  different  appearance,  are  produced.     The 
calyx  remains  permanently  closed,  while  the  corolla  is  un- 
developed.    Only  two  stamens  reach  maturity,  and  their 


THE  FLOWER  119 

anthers  are  pressed  against  the  end  of  the  style.  The 
pollen  grains  are  few  and  unusually  small.  Fertilization 
is  effected  in  the  closed  flowers,  and  abundant  seed  results, 
the  pods  seeding  far  more  freely  indeed  than  those  of  the 
ordinary  flowers.  In  some  species  of  Violet,  these  deistog- 
amous  flowers  are  concealed  under  the  leaves,  or  are  borne 
on  runners  underground. 

232.  Self-fertilization    prevented.  —  Many   flowers   are 
habitually  fertilized  either  (1)  by  their  own,  or  (2)  by 
foreign  pollen,  —  sometimes  in  one  way,  sometimes  in  the 
other,  as  chance  decides.     In  the  great  majority  of  flower- 
ing plants,  however,  cross-fertilization  is  the  rule.     Self- 
fertilization  may  be  absolutely  prevented.     This  must  be 
the  case  when  the  flower  bears  only  pistils  (is  pistillate), 
or  stamens  (is  staminate).     Sometimes  the  staminate  and 
pistillate  flowers  are  produced  on  separate  individual  plants 
(when  the  plants  are  said  to  be  dioecious)  ;  sometimes  on 
the    same   plant    (when   the    species  is  monoecious).     An 
equally  sure  mode  of  preventing  self-fertilization  is  seen 
where  the  pistils  and  stamens,  though  both  present,  are 
active  at  different  times.     This  may  well  be  illustrated 
by  the  common  Plantain.     The  flowers  are  borne  on  long 
spikes.       The    unfolding  of   the  flowers  "  proceeds  from 
base  to  apex  of  the  spike   in  regular   order,  and  rather 
slowly.     While   the    anthers   are    still    in   the    unopened 
corolla  and  on  short  filaments,  the  long  and  slender  hairy 
stigma  projects  from  the  tip  and  is  receiving  pollen  blown 
to  it  from  neighboring  plants  or  spikes  :  a  day  or  two  after- 
wards, the  corolla  opens,  the  filaments  greatly  lengthen, 
and  the  four  anthers  now  pendent  from  them  give  their 
light  pollen  to  the  wind  ;  but  the  stigmas  of  that  flower 
and  of   all   below  it  on  that  spike  are  withered  or  past 
receiving  pollen."1 

233.  When  the  stamens  mature  first,  as  in  many  flowers, 
the  condition  is  termed  proterandry.     In  the  opposite  case, 
proterogyny,  which  is  less  usual,  the  pistils  have  been  fertil- 
ized or  are  no  longer  receptive  by  the  time  the  anthers  open. 

i  Asa  Gray,  "  Structural  Botany,"  p.  219. 


OF  THE 

UNIVERSITY 

120  THE  FLOWER 


165.  A  pollen  grain  of  the 
Pine,  provided  with 
two  air-filled  vesi- 
cles to  give  buoyancy 
in  the  air. 


234.  Agencies  and  adaptations  for  intercrossing.  —  The 
agents  serving  to  transport  pollen  from  flower  to  flower 
are  wind,  water,  and  small  animals  (mainly  insects). 

235.  Pollination    by  wind.  —  Among    the    adaptations 
displayed  by  wind-pollinated  flowers  are  to  be  mentioned 
the  character  and  quantity  of  the  pollen  produced.     Thus 

the  pollen  grain  of  the  Pine  con- 
sists of  three  compartments,  the 
two  lateral  ones  empty  and  serving 
as  wings  (Fig.  165).  "The  im- 
mense abundance  of  pollen,  its 
lightness,  and  its  free  and  far  diffu- 
sion through  the  air  in  Pines,  Firs, 
and  other  Coniferse,  are  familiar. 
Their  pollen  fills  the  air  of  a  forest 
during  anthesis  ;  arid  the  '  showers 

of  sulphur,'  popularly  so-called,  the  yellow  powder  which 
after  a. transient  shower  accumulates  as 
a  scum  on  the  surface  of  water  several 
or  many  miles  from  the  nearest  source, 
testifies  to  these  particulars."1  All  cat- 
kin-bearing trees  —  except  Willows  — 
and  most  grasses  and  sedges  are  wiiid- 
pollinated.  Their  flowers  are  mostly 
dull-colored,  odorless,  and 
destitute  of  honey.  The 
stigmas  are  relatively 
prominent  and  apt  to  be 
plumose  (Fig.  166).  The 
anthers  are  often  poised 
on  the  tip  of  the  filament 
(Fig.  167),  so  that  they 
are  shaken  by  the  wind. 
As  they  turn  readily  in  all  directions 
they  are  said  to  be  versatile. 

236.  The  pollen  of  aquatic  plants  is   1G6   piumeiike    stig- 
sometimes    carried   from   one   flower   to        mas  of  a  srass- 

1  Gray,  "Structural  Botany,"  p.  217. 


167.  A  versatile 
anther. 


THE'  FLOWER 


121 


another  by  the  water,  or  water  and  wind  together  ;  the 
staminate  flowers  of  the  fresh- water  Eel-grass,  for  instance, 
after  being  detached  from  the  submerged  heads,  are  driven 
like  minute  rafts  before  the  wind,  and  collect  about  the 
much  larger  pistillate  flowers  on  the  surface.1 

237.  A  few  species  of  plants  are  regularly  cross-polli- 
nated    by    snails,    and 

others  by  birds. 

238.  Pollination      by 
insects.  —  Cross-fertili- 
zation      in      flowering 
plants  is  brought  about 
by  aid  of  insects  far  more 
frequently  than   by  all 
other  agencies  combined. 
A  few  cases  will  be  de- 
scribed in  some  detail. 

239.  Lady's     Slipper 
(Qypripedium)  and  the 
South  American  Seleni- 
pedium,  Fig.  168,  show 
a  very  perfect  mode  of 
compelling   the    insects 
that  visit  them  to  serve 
as  pollen  bearers.     One 
of  the  petals  is  shaped 
into  a  sac,  or  labellum, 

Open  above  an  don  either    168.  Flower    of    South    American    Seleni- 

side  near  the  base  (0). 

The    bee    alighting    on 

this  labellum  in  search 

of  the  honey  secreted  by 

glandular  hairs  within, 

and  entering  through  the  main  opening,  is  prevented  by 

the  incurved  edges  of  the  latter,  as  well  as  by  the  depth 

of  the  labellum,  from  escaping  except  by  one  of  the  two 


pedium  SchKmU,  The  dotted  lines 
with  arrow  tips  show  the  course  fol- 
lowed by  a  visiting  bee.  In  b,  the 
flower  is  seen  from  the  side,  the 
labellum,  or  saccate  petal,  being  cut 
open ;  p,  a  pollen  mass ;  s,  the  stigma ; 
e,  exits. 


1  See  Kerner  and  Oliver,  "Natural  History  of  Plants,"  Vol.  II.,  p.  132. 


122 


THE  FLOWER 


posterior  openings,  or  exits  (<?).  As  it  emerges  through 
this  rather  narrow  portal,  it  brushes  against  one  of  the 
pollen  masses  (jt?),  which  adheres  to  its  head  or  shoulder, 
In  the  next  flower  visited,  the  bee  in  leaving  encounters 
the  stigma  (s),  and  leaves  on  the  surface  some  of  the  pollen 
brought  from  the  former  flower.  Finally  succeeding  in 
crawling  past  this  obstacle,  it  brushes  a  pollen  mass  from 
this  flower,  to  be  carried  to  the  next ;  and  so  passes  about, 
always  taking  away  pollen,  but  not  depositing  it  upon 
the  stigma  of  the  same  flower. 

240.  Sage  (Salvia,  Fig.  169 1).— The  corolla  is  two- 
lipped,  as  nearly  always  in  the  Mint  family,  the  lower  lip 
serving  as  a  convenient  landing  stage  for  insects,  while  the 
upper,  erect  and  arched,  incloses  the  two  anthers  (#) .  The 

flower  is  proterandrous, 
and  at  the  period  rep- 
resented in  the  figure 
the  stigma  is  seen  pro- 
truding from  the  upper 
lip,  its  two  branches 
folded  together.  The 
stamens  are  inserted 
on  the  sides  of  the 
narrow  throat  and 
are  hinged  near  the 
point  of  insertion. 
Each  bears  a  projec- 


B 


169. 


Mechanism  of  the  flower  of  Salvia;  a, 
pollen  sacs  of  the  anthers,  hidden 
under  the  upper  lip  of  the  corolla;  a', 
their  position  when  dusting  the  back 
or  sides  of  a  hee ;  c,  lobes  against 
which  the  bee  pushes  in  thrusting  its  tion  (<?)  standing  Out 
head  into  the  throat  of  the  corolla;  j  nartlv  hlnpkino- 

s,  stigma,  immature ;  *',  stigma  when  ™ 

mature.  In  A  the  stamens  ai*e  seen, 
removed  from  the  corolla ;  /,  filament 
on  which  the  anther  turns. 


the  throat.  When  a 
bee  pushes  its  head 
into  the  corolla  tube, 

these  projections  are  pushed  back,  and  the  whole  upper 
parts  of  the  stamens  are  rotated  on  the  hinges.  The 
pollen  sacs,  heretofore  concealed  under  the  hood,  are 

1  From  M  tiller's  "  Fertilization  of  Flowers,"  by  courtesy  of  the  Macmil- 
lan  Company,  publishers,  New  York.  The  book  is  a  valuable  reference 
work. 


THE  FLOWER 


12S 


170.   Partridge    Berry,  with    two    forms    of 
flowers. 


brought  down  into  the  position  a'  and  dust  the  bee's  back 
with  pollen.  When  the  bee  withdraws  its  head,  the 
anthers  resume  their  former  station.  At  a  later  stage, 
after  the  pollen  is  exhausted  or  the  anther  withered,  the 
stigma  becomes  receptive.  It  then  occupies  the  position 
»',  and  its  branches 
spread  to  brush  pollen 
from  the  back  of  a 
subsequent  visitor. 

241.  Partridge   Ber- 
ry (^Mitchell  a,    Fig. 
170).  —  The        plant 
grows   abundantly,  as 
a   small   trailing  herb 
with  evergreen  leaves, 

in  open  woods.     The  blossoms  are  of  two  forms  ;  namely, 
one  form  (a)  with  long  style  and  low  stamens,  the  other 

(5)  with  short  style  and  high 
stamens  (Fig.  171).  The  sta- 
mens of  form  a  are  at  about 
the  same  level  as  the  stigma 
of  form  b  ;  and  the  stamens 
of  b  are  level  with  the  stigma 
of  a.  An  insect  brushing  the 
stamens  of  b  with  its  sides 
will  subsequently  bring  these 
pollen-dusted  sides  in  contact 

a,  long-styled  form  ;  &,  short-    with  the  stigma  of   a.     The 
styled  form,  of  flower  in  the    proboscis  of  the  insect,  smeared 

Partridge  Berry.  ^ 

with  pollen  from  the  stamens 

,  will  leave  some  of  it  on  the  stigma  of  b.  When 
a  species  of  plants  bears  two  sorts  of  flowers,  as  regards 
the  relative  lengths  of  stamens  and  style,  the  flowers  are 
said  to  be  dimorphic.  In  many  dimorphic  flowers  the  pol- 
len of  a  differs  in  size  from  that  of  b  ;  and  neither  kind  of 
pollen  is  capable  of  fertilizing  the  flower  that  produces  it. 

242.  The  opening  and  closing  of  flowers,    according   to 
the  habits  of  the  insects  that  pollinate  them,  —  opening  by 


of 


124  THE  FLO  WEE 

day  when  pollinated  by  diurnal,  at  night  when  by  nocturnal, 
insects,  —  may  be  illustrated  from  a  flower  described  by 
Sir  John  Lubbock.1  It  is  the  Nottingham  Catchfly,  a 
British  and  European  plant  related  to  our  Chickweeds 
and  Pinks.  "  Each  flower  lasts  three  days,  or  rather  three 
nights.  The  stamens  are  ten  in  number,  arranged  in  two 
sets ;  the  one  set  standing  in  front  of  the  sepals,  the  other 
in  front  of  the  petals.  Like  other  night  flowers,  it  is 
white,  and  opens  toward  evening,  when  it  also  becomes 
very  fragrant.  The  first  evening,  toward  dusk,  the  five 
stamens  in  front  of  the  sepals  grow  very  rapidly  for  about 
two  hours,  so  that  they  emerge  from  the  flower ;  the  pollen 
ripens,  and  is  exposed  by  the  bursting  of  the  anther.  So 
the  flower  remains  through  the  night,  very  attractive  to, 
and  much  visited  by,  moths.  Toward  three  in  the  morn- 
ing the  scent  ceases,  the  anthers  begin  to  shrivel  up  or 
drop  off,  the  filaments  turn  themselves  outward,  so  as  to 
be  out  of  the  way,  while  the  petals,  on  the  contrary,  begin 
to  roll  themselves  up,  so  that  by  daylight  they  close  the 
aperture  of  the  flower,  and  present  only  their  brownish 
green  under  sides  to  view ;  which,  moreover,  are  thrown 
into  numerous  wrinkles.  Thus,  by  the  morning's  light, 
the  flower  has  all  the  appearance  of  being  faded.  It  has 
no  smell,  and  the  honey  is  covered  over  by  the  petals. 
So  it  remains  all  day.  Toward  evening,  however,  every- 
thing is  changed.  The  petals  unfold  themselves  ;  by  eight 
o'clock  the  flower  is  as  fragrant  as  before,  the  second  set 
of  stamens  have  rapidly  grown,  their  anthers  are  open, 
and  the  pollen  again  exposed.  By  morning  the  flower  is 
again  '  asleep,'  the  anthers  are  shriveled,  the  scent  has 
ceased,  and  the  petals  rolled  up  as  before.  The  third 
evening,  again  the  same  process  occurs,  but  this  time  it 
is  the  pistil  which  grows :  the  long  spiral  stigmas  on  the 
third  evening  take  the  position  which  on  the  previous 
two  had  been  occupied  by  anthers,  and  can  hardly  fail  to 
be  dusted  by  moths  with  pollen  brought  from  another 
flower." 

1  Lubbock,  "Dowers,  Fruits,  and  Leaves,"  Macinillan,  1894,  p.  40. 


THE  FLOWER  125 

243.  The    object    of    the    insects'    visits   is    usually    a 
sweetish  liquid,  the  nectar  secreted  by  glands  —  commonly 
in  the  forms  of  swellings  of  the  tissue  of  the  receptacle  — 
at  the  base  of  the  flower.     These  are  the  nectaries.     In 
flowers  with  spurred  petals,  like  the  Columbine,  the  nectar 
is  secreted  at  the  end  of  the  spur,  whence  it  can  be  sucked 
up  only  by  the  long-tongued  insects,  which  are  the  most 
effective  in  transferring  the  pollen  of  these  plants. 

244.  In  addition  to  nectar,  the  pollen  itself,  a  highly 
nutritious  product,  is  sought  by  many  insects. 

245.  Protection  of  the  nectar.  —  Such  a  desirable  food 
as  the  nectar  is  sure  to  be  attractive  to  insects  which,  by 
reason  of  their  size  or  habits,  are  not  likely  to  make  any 
return  of  service  to  the  plant.     Ants,  for  instance,  travel 
all  over  the  herbage  in  the  vicinity  of  their  nests  in  search 
of  food.     Happening  upon  the  wells  of  honey  within  the 
flower,  they  would  drink  their  fill,  and  perhaps  bring  their 
fellow-ants  to  the  place,  as  their  custom  is,  with  the  result 
that  the  flower  would  be  drained  of  its  nectar;  but  these 
visitors  would  be  too  small,  in  the  case  of  many  flowers, 
to  brush  the  pollen  from  the  tall  stalked  stamens,  or  de- 
posit it  on  the  stigma  at  the  summit  of  the  lengthened  style. 
And,  further,  even  were  it  possible  for  transference  to  be 
made  by  the  adherence  of  the  pollen  to  the  bodies  of  the  ants, 
the  slow  movements  of  these  insects,  their  short-sightedness 
and  blind  wanderings,  and  their  indiscriminate  visiting  of 
all  sorts  of  plants  would  make  them  unprofitable  carriers, 
as  regards  any  one  vegetable  species,  when  compared  with 
swift-flying,  long-sighted,  and  often  times  discriminating 
insects  like  the  various  bees,  butterflies,  and  moths. 

246.  Consequently,    very   many    flowers   are    fortified 
against  the  invasions  of  the  ants  —  and  other  undesirable 
visitors.     One  of  the  common  and  effective  methods  of 
defense  is  a  coating  of   downward-pointing,  or  in  cases 
stioky,  hairs  on  the  flower  stalk  or  on  the  calyx.      In 
some  instances  the  secretion  from  the  hairs  not  only  pre- 
vents insects  from  going  farther  up  the  stalk,  but  holds 
any  trespasser  firmly,  so  causing  its  death. 


126 


THE  FLO  WEE 


172.  Two  of  the  florets  in  a  head  of  Dandelion 
(diagrammatic) . 


247.    The  protection  of  the  nectar  from  rain  is  effected 
sometimes   by  the   habitually   drooping   attitude   of   the 

flower,  sometimes 
by  the  bending  or 
bowing  of  the 
flower  stalk  on  the 
approach  of  rain, 
sometimes  by  some 
special  construc- 
tion of  the  flower. 
248.  The  group- 
ing of  flowers  in  a 
specialized  part  of 
the  shoot  in  a  man- 
ner likely  to  secure  the  attention  of  insects,  and  so  lead 
to  the  process  of  cross-fertilization,  should  be  noted.  The 
Dandelion  (Fig.  172)  and  the  Jack-in-the-pulpit  (Fig.  173) 
may  be  taken  as  illustrations.  In 
both  these  cases  clusters  of  flowers 
are  commonly  mistaken  for  single 
flowers.  The  apparent  "petals"  of 
the  Dandelion  head  are  the  several 
separate  corollas  of  as  many  small 
flowers  or  florets.  On  close  examina- 
tion each  of  these  florets  is  seen  to 
possess  its  own  two-parted  stigma, 
and  andrcecium  of  five  stamens  united 
around  the  style.  What  might  pass 
at  a  casual  glance  for  a  calyx,  sur- 
rounding the  whole  head,  is  a  collec- 
tion of  subtending  leaves  (bracts)  173> 
serving  to  protect  the  bud. 

249.  In  the  Jack-in-the-pulpit 
(Fig.  173),  a  fleshy  spike  of  small 
flowers  (termed  a  spadix)  is  sur- 
rounded and  overarched  by  a  single 
more  or  less  striped  or  colored  bract  (termed  in  sucli 
a  case  a  spathe). 


The  bract  (spathe) 
partly  cut  away 
helow  to  show  the 
fleshy  spike  (spa- 
dix)  of  flowers 
which  it  surrounds. 


THE  FLOWER  127 

250.  In  both  these  cases,  and  countless  others,  the  inflo- 
rescence —  mode  of  arrangement  of  the  flowers  —  is  deter- 
mined by  the  need  of  cross-fertilization. 

EFFECT  OF  CROSSING 

251.  The  arrangements   for   cross-fertilization   are   ex- 
tremely varied  and  in  many  cases  extraordinarily  compli- 
cated.    It  could  not  well  be  doubted  that  such  elaboration 
has  been  evolved  because  some  important  benefit  is  derived 
from  intercrossing.     And  experiment  goes  to  show  that 
this  is  actually  the  case.      When  seeds  derived  from  both 
self-fertilization  and  cross-fertilization  of  the  same  plant  are 
grown  side  by  side,  the  offspring  of  cross-fertilization  gen- 
erally outstrips  that  produced  by  self-fertilization.      In 
spite  of  the  fact  that  a  small  number  of  species  are  propa- 
gated indefinitely  without  intercrossing  (seedless  plants, 
reproduced  vegetatively),  and  as  far  as  is  known  without 
harmful  results,  the  important  truth   remains  that  inter- 
crossing is  a  means  of  giving  increased  vigor  to  seedlings. 

Supplementary  Reading 

1.  Adaptations  for   Securing  Intercrossing.     Gray's    "Structural 
Botany,"  p.  220  and  following. 

2.  The  Pollination  of  Orchids.     C.  M.  Weed's  "  Ten  New  England 
Blossoms,"  Nos.  VI.  and  VII. 

3.  "  The  Mayflower."     Same  source,  No.  II. 

4.  The  Industriousness  of  Bees,  and  the  Perception  of  Color  by 
Insects.     Sir  John  Lubbock's  "  Flowers,  Fruits,  and  Leaves,"  pp.  11-14. 

Supplementary  Studies:    Fieldwork  on  the  Ecology 
of  the  Flower 

252.  The  account  of  adaptations  to  secure  cross-fertilization  given  in 
this  chapter  is  necessarily  brief,  hardly  more  than  suggesting  some  general 
principles.  Subjects  not  touched,  but  well  worth  study  in  the  field,  are : 
Attraction  of  Insects  («)  by  colors,  (6)  by  grouping  flowers,  (c)  by  scent ; 
Opening  of  Flowers  at  special  times  to  receive  special  classes  of  insects  ; 
Guides  to  Honey,  (a)  spots  and  streaks,  (6)  conformation  of  floral  parts  ; 
Reward  to  Insects,  (a)  honey  and  sap  (with  distribution  and  form  of 
secreting  organs),  (6)  pollen,  (c)  edible  tissue,  (of)  shelter;  Dusting  the 
Insect,  (a)  by  irritable  stamens  (Barberry),  (5)  by  springing  stamens 


128  THE  FLOWER 

(Mountain  Laurel),  (c)  by  explosion  ;  Movement  of  Stamens  anl  Style, 
(a)  to  avoid,  (5)  to  secure  self-fertilization  ;  Protection  of  Pollen  and 
Honey,  (a)  against  unwelcome  visitors,  (6)  against  weather,  (1)  by  shape 
and  position  of  the  flower,  (2)  by  bowing  of  the  flower  stem  at  times. 
This  outline  will  serve  as  a  working  basis,  which  may  be  extended  to 
include  cases  that  arise  in  actual  observation. 

TERMINOLOGY  OF  THE   FLOWER 

[Inserted  for  the  use  of  classes  that  are  to  take  up  the  determination  of 
flowering  plants.] 

For  the  student  who  is  preparing  to  study  Systematic  Botany,  a 
knowledge  of  the  descriptive  terms  applied  to  the  parts  of  the  flower 
and  the  inflorescence  is  indispensable.  The  relationships  of  plants 
are  more  easily  studied  in  their  flowers  than  in  the  vegetative  parts, 
because  in  the  flower  there  are  brought  together  in  small  compass  so 
many  sharply  marked  and  readily  described  characteristics,  varying 
slowly,  for  the  most  part,  through  wide  ranges  of  related  plants. 
Descriptions  written  to  enable  one  to  determine  the  names  of  the 
plants  that  he  collects  are  accordingly  based  very  largely  on  the 
flower.  Many  of  the  more  usual  terms  —  not  already  given  —  are  now 
to  be  explained. 

253.  Terms  relating  to  the  general  plan  of  the  flower.  Flowers 
are  said  to  be  :  — 

Perfect  (hermaphrodite)  when  provided  with  both  kinds  of  essential 
organs,  i.e.,  with  both  stamens  and  pistils. 

Complete,  when,  besides,  they  have  the  two  sets  of  floral  envelopes ; 
namely,  calyx  and  corolla.  Such  are  completely  furnished  with  all 
that  belongs  to  a  flower. 

Regular  or  actinomorphic,  when  all  the  parts  of  each  set  are  alike  in 
shape  and  size.  Flowers  of  this  type  can  be  divided  by  at  least  two 

planes  into  equal  and  symmetrical 
parts. 

Imperfect,  or  better,  unisexual, 
flowers,  in  which  some  flowers  lack 
the  stamens,  others  the  pistils. 
Taking  hermaphrodite  flowers  as 
the  pattern,  it  is  natural  to  say  that 
the  missing  organs  are  suppressed. 
This  expression  is  justified  in  the 
very  numerous  cases  in  which  the 
missing  parts  are  abortive,  that  is, 
are  represented  by  rudiments  or 

vestiges,  which  serve  to  exemplify 
174.   Unisexual  flowers  of  the  Castor     , ,         ,  ,, ,         ,  , 

Oil  plant  ;p,  pistillate,  a,  stem-     the    Plan'  altho"Sh  useless  as   to 
inate  flowers.  office.     Unisexual  flowers  are  :  — 


THE  FLOWER 


129 


175. 


Unisexual  flowers  of 
Moonseed ,  borne  on 
different  plants. 


Monoecious  {i.e.,  of  one  household),  when  flowers  of  both  sorts  or 
sexes  are  produced  by  the  same  individual  plant,  as  in  the  Ricinus  or 
Castor  Oil  plant  (Fig.  174). 

Dioecious  {i.e.,  of  separate  households), 
when  the  two  kinds  are  borne  on  different 
plants ;  as  in  Willows,  Poplars,  and  Moon- 
seed  (Fig.  175). 

Polygamous,  when  the  flowers  are  some  of 
them  perfect,  and  some  staminate  or  pistil- 
late only. 

254.  A  blossom  having  stamens  and  no 
pistil  is  a  staminate  or  male  flower.  Sometimes  it  is  called  a  sterile 
flower,  not  appropriately,  for  other  flowers  may  equally  be  sterile. 
One  having  pistil  but  no  stamens  is  a  pistillate  or  female  flower. 

255.    Incomplete  flowers  are  so  named  in  con- 
tradistinction   to    complete :    they 
want   either    one   or   both   of    the 
floral    envelopes.      Those    of    the 
Anemone    (Fig.    176)    are    incom- 
plete, having  calyx  but  no  corolla. 
The  sepals,  however,  are  highly  col- 
ored  and  petal-like.     The  flowers 
of   Saururus   or   Lizard's    tail,    although    perfect, 
have  neither  calyx  nor  corolla  (Fig.  177).     Incomplete  flowers,  accord- 
ingly, ar-e:  — 

Naked  or  achlamydeous,  destitute  of    both  floral  envelopes,  as  in 

Fig.  177,  or— 

Apetalous,  when  wanting  only 
the  corolla.  The  case  of  corolla 
present  and  calyx  wholly  wanting 
is  extremely  rare,  although  there 
are  seeming  instances.  In  fact,  a 
single  or  simple  perianth  is  taken 
to  be  a  calyx,  unless  the  absence 
or  abortion  of  a  calyx  can  be 
made  evident. 

256.  In  contradistinction  to 
regular  and  symmetrical,  very 
many  flowers  are  :  — 

Irregular,  that  is,  with  the  mem- 
bers of  some  or  all  of  the  floral 
circles  unequal  or  dissimilar.  A 
special  and  important  case  of  floral 
irregularity  is  shown  by  — 

Zygomorpliic  flowers  which,  like 


ITS 


181 


178,  179.  Mustard:  178,  flower;  179, 
its  stamens  and  pistil  separate 
and  enlarged. 

180,181.  Violet:  180,  flower;  181,  its 
calyx  and  corolla  displayed  ;  the 
five  smaller  parts  are  the  sepals  ; 
the  five  intervening  larger  ones 
are  the  petals. 

OUT.  OF  BOT.  -  9 


130 


THE  FLOWER 


most  of  those  in  the  Pulse  and  Mint  families,  can  be  divided  by  one 
and  only  one  plane  into  two  equal  parts. 

257.  The  relation  of  the  perianth  and  stamens  to  the  pistil  is  ex- 
pressed by  the  terms  hypogynous  (i.e.  under  the  pistil),  when  they  are 
all  free,  that  is,  not  adnate  to  pistil  or  united  with  each  other,  as  in 
Fig.  182. 

Perigynous  (around  the  pistil),  when  adnate  to  each  other,  that 
is,  when  petals  and  stamens  are  inserted  or  borne  on  the  calyx,  whether 


187 


as  in  Cherry  flowers  (Fig.  183)  they  are  free  from  the  pistil,  or  as  in 
Purslane  and  Hawthorn  (Figs.  184, 185)  they  are  also  adnate  below  to 
the  ovary. 

Epigynous  (on  the  ovary),  when  so  adnate  that  all  these  parts  appear 
to  arise  from  the  very  summit  of  the  ovary,  as  in  Fig.  186.  The  last 
two  terms  are  not  very  definitely  distinguished. 

258.  Position  of  the  parts  of  the  flower.  —  The  terms  superior  and 
inferior,  or  upper  and  lower,  are  also  used  to  indicate  the  relative 
position  of  the  parts  of  a  flower  in  reference  to  the  axis  of  inflores- 
cence. An  axillary  flower  stands  between  the  bract  or  leaf  which 
subtends  it  and  the  axis  or  stem  which  bears  this  bract  or  leaf.  This 
is  represented  in  sectional  diagrams  (as  in  Figs.  187,  188)  by  a  trans- 
verse line  for  the  bract,  and  a  small  circle  for  the  axis  of  inflorescence. 


THE  FLO  WEE 


131 


Now  the  side  of  the  blossom  which  faces  the  bract  is  the  anterior,  or 
inferior,  or  lower  side;  while  the  side  next  the  axis  is  the  posterior, 
or  superior,  or  upper  side  of  the  flower. 

259.  So,  in  the  labiate  corolla  (Figs.  198,  200), 
the  lip  which  is  composed  of  three  of  the  five 
petals  is  the  anterior,  or  inferior,  or  lower  lip;  the 
other  is  the  posterior,  or  superior,  or  upper  lip. 

260.  Terms  applicable  to  corolla  and  calyx. — 
Gamopetalous,  said  of  a  corolla  the  petals  of  which 
are  coalescent  into  one  body,  whether  only  at  base 
or  higher.      The  union  may  extend  to  the  very 
summit  as  in  Morning  Glory,  the  Datura  (Fig. 
189),  and  the  like,  so  that  the  number  of  petals 
in  it  may  not  be  apparent.      The  old  name  for 
this   was    monopetalous,    but    that    means    "one- 
petaled";     while    gamopetalous    means    "petals 
united,"  and  therefore  is  the  proper  term. 

Polypetalous  is  the  counterpart  term,  to  denote 

a  corolla  of  distinct,  that  is,  separate  petals.  As  it  means  "  many- 
petaled,"  it  is  not  the  best  possible  name,  but  it  is  the  old  one  and 
in  almost  universal  use. 

Gamosepalous  applies  to  the  calyx  when  the  sepals  are  in  this  way 
united. 

Polysepalous,  to  the  calyx  when  of  separate  sepals. 

261.  Degree  of  union  or  of  separation  in  descriptive  botany  is  ex- 
pressed in  the  same  way  as  is  the  lobing  of  leaves.     See  Figs.  116-123, 

and  the  explanations. 

262.  A  corolla  when 
gamopetalous  commonly 
shows  a  distinction  (well 
marked  in  Figs.  191- 
193)  between  a  con- 
tracted tubular  portion 
below,  the  TUBE,  and  the 
spreading  part  above, 

the  BORDER  or  LIMB.  The  junction  between  tube  and  limb,  or  a 
more  or  less  enlarged  upper  portion  of  the  tube  between  the  two, 
is  the  THROAT.  The  same  is  true  of  the  calyx. 

263.    Some  names  are  given  to  particular  forms  of  the  gamopeta- 
lous corolla,  applicable  also  to  a  gamosepalous  calyx,  such  as 

Wheel-shaped,  or  rotate,  when  spreading 
out  at  once,  without  a  tube  or  with  a  very  short 
one,  something  in  the  shape  of  a  wheel  or  of 
its  diverging  spokes  (Figs.  194,  195). 

Salver-shaped,  or  salver-formed,  when  a  flat^          194  195 


132 


THE  FLOWER 


196      197          198  199          200 

196-200.  Corollas :  196,  a  Campanula  or  Hare- 
bell, with  a  campanulate  or  bell-shaped 
corolla ;  197,  a  Phlox,  with  salver-shaped 
corolla ;  198,  Dead  Nettle  (Lamium) ,  with 
labiate  ringent  (or  gaping)  corolla ;  199, 
Snapdragon,  with  labiate  personate  co- 
rolla; 200,  Toadflax,  with  a  similar 
corolla  spurred  at  the  base. 


201 


spreading  border  is  raised  on  a  narrow  tube,  from  which  it  diverges 

at  right  angles,  like  the 
salver  represented  in  old 
pictures,  with  a  slender 
handle  beneath  (Figs. 
191-193,  197). 

Sell-shaped,  or  cam- 
panulate, where  a  short 
and  broad  tube  widens 
upward,  in  the  shape  of  a 
bell,  as  in  Fig.  196. 

Funnel  -  shaped,  or 
funnel-form,  gradually 
spreading  at  the  summit 
of  a  tube  which  is  narrow 
below,  in  the  shape  of 
a  funnel  or  tunnel,  as 

in  the  corolla  of  the  common  Morning  Glory  and  of  the  Datura 

(Fig.  189). 

Tubular;  when  prolonged  into  a  tube,  with 

little  or  no  spreading  at  the  border,  as  in  the 

calyx  of  Datura  (Fig.  189). 

264.  Although     sepals    and     petals     are 
usually  all  blade  or  lamina,  like   a  sessile 
leaf,  yet  they  may  have  a  contracted   and 
stalklike  base,  answering  to  petiole.     This  is 
called  CLAW,  in  Latin  unguis.      Unguiculate 
petals   are   universal    and   strongly   marked 
in  the    Pink  tribe,   as   in    Soapwort   (Fig. 
190). 

265.  Such  petals,  and  various  others,  may   201-202.  Crowns:  201, un- 
have  an  outgrowth  of  the  inner  face  into  an  guiculate  (clawed) 
appendage  or  fringe,  as  in  Soapwort,  and  in               petal  of  a  Silene ; 
Silene  (Fig.  201),  where  it  is  at  the  junction 

of  claw  and  blade.  This  is  called  a  CROWN, 
or  corona.  In  Passion  Flowers  (Fig.  202) 
the  crown  consists  of  numerous  threads  on 
the  base  of  each  petal. 

266.  Papilionaceous  corolla  ( Figs.  203, 204) .  —  This  is  polypetalous, 
except  that  two  of  the  petals  cohere,  usually  but  slightly.     It  belongs 
only  to  the  Leguminous  or  Pulse  family.      The  name  means  butter- 
flylike ;  but  the  likeness  is  hardly  obvious.    The  names  of  the  five  petals 
of  the  papilionaceous  corolla  are  curiously  incongruous.     They  are, 

The  STANDARD  or  banner  (vexillum),  the  large  upper  petal  which  is 
external  in  the  bud  and  wrapped  around  the  others. 


crown  ;  202,  a  small 
Passion  Flower, 
with  crown  of  slen- 
der threads. 


THE  FLOW  EH 


133 


The  WINGS  (ate),  the  pair  of  side  petals,  of  quite  different  shape 

from  the  standard. 

The   KEEL    (carina),   the   two   lower  and 

usually  smallest  petals ;  these  are  lightly  coa- 

lescent  into  a  body  which  bears  some  likeness, 

not  to  the  keel,  but  to  the  prow  of  a  boat ;  and 

this  incloses  the  stamens  and  pistil.      A  Pea 

blossom  is  a  typical  example. 
267.   Labiate  corolla  (Figs.  198-200),  which 

would  more  properly  have  been  called  bilabiate, 

that  is,  two-lipped.     This  is  a  common  form 

of  gamopetalous    corolla;    and   the    calyx   is 

often  bilabiate  also.     These  flowers  are  all  on 

the  plan  of  five;  and  the  irregularity  in  the 

corolla  is  owing  to  unequal  union  of  the  petals 

as  well  as  to  diversity  of  form.      The  two 

petals  of  the  upper  or  posterior  side  of  the 

flower  unite  with  each  other  higher  up  than 

with  the  lateral  petals  (in  Fig.  198,  quite  to 

the  top),  forming  the  upper  lip ;   the  lateral    203,  204. 

and  the  lower  similarly  unite  to  form  the  lower 

Up.    The  single  notch  which  is  generally  found 

at  the  summit  of  the  upper  lip,  and  the  two 

notches  of  the  lower  lip,  or  in  other  words  the 

two  lobes  of  the  upper  and  the  three  of  the 

lower  lip,  reveal  the  real  composition.    So  also 

does  the  alternation  of  these  five  parts  with  those  of  the  calyx  outside. 

When  the  calyx  is  also  bilabiate,  as  in  the  Sage,  this  alternation  gives 

three  lobes  or  sepals  to  the  upper  and  two  to  the  lower  lip.     Two 

forms  of  the  labiate  corolla  have  been  designated,  viz. :  — 
Ringent  or  gaping,  when  the  orifice  is  wide  open  (Fig.  198). 
Personate  or  masked,  when  a  protuberance  or  intrusion  of  the  base 

of  the  lower  lip  (called  a  palate)  projects  over  or  closes  the  orifice, 

as  in  Snapdragon  and  Toadflax  (Figs. 
199-200 .. 

268.  Ligulate  corolla.  — The  ligu- 
late  or  strap-shaped  corolla  mainly 
belongs  to  the  family  of  Compositae, 
in  which  numerous  small  floweia  are 
gathered  into  a  head,  within  an  involucre 
that  imitates  a  calyx.  It  is  well  exem- 
plified in  the  Dandelion  and  in  Chiccory 
(Fig.  205).  Each  one  of  these  straps  or 
ligules,  looking  like  so  many  petals,  is 

the  corolla  of  a  distinct  flower  :  the  base  is  a  short  tube,  which  opens 


ous  corolla :  203, 
front  view ;  204,  the 
parts  of  the  same 
displayed :  s,  stand- 
ard, or  vexillura  ; 
w,  wings,  or  alse; 
k,  keel,  o/  carina. 


205 


134 


THE  FLOWER 


206.  A  slice  of  the  Coreopsis  head 
enlarged,  with  one  tubular  per- 
fect flower  (a)  left  standing 
on  the  receptacle,  with  its 
bractlet  or  chaff  (6),  one  ligu- 
late  and  neutral  ray  flower, 
and  part  of  another  (cc) ;  dd, 
section  of  bracts  or  leaves  of 
the  involucre. 


out  into  the  ligule ;  the  five  minute  teeth  at  the  end  indicate  the 
number  of  constituent  petals.  So  this  is  a  kind  of  gamopetalous 
corolla,  which  is  open  along  one  side  nearly  to  the  base,  and  outspread. 

269.  In  Asters,  Daisies,  Sunflower,  Coreopsis  (Fig.  206),  and  the 

like,  only  the  marginal  (or  ray)  co- 
rollas are  ligulate ;  the  rest  (those 
of  the  disk)  are  regularly  gamo- 
petalous, tubular,  and  five-lobed 
at  summit;  but  they  are  small 
and  individually  inconspicuous, 
only  the  ray  flowers  making  a 
show.  In  fact,  those  of  Coreopsis 
and  of  Sunflower  are  simply  for 
show,  these  ray  flowers  being  not 
only  sterile,  but  neutral,  that  is, 
having  neither  stamens  nor  pistil. 
But  in  Asters,  Daisies,  Golden- 
rods,  and  the  like,  these  ray  flowers 

are  pistillate  and  fertile,  serving  therefore  for  seed  bearing  as  well 

as  for  show. 

270.  The  Stamens.  —  First  as  regards  their  insertion,  or  place  of 
attachment. 

The  stamens  usually  go  with  the  petals  rather  than  with  the  pistil, 
when  adherent  to  either.     Not  rarely  they  are 

Epipetalous,  that  is,  inserted  on  (or   adnate  to)  the  corolla,   as 
in  Fig.  171.     When  free  from  the  corolla,  they  may  be 

Hypogynous,  inserted  on  the  receptacle  under 
the  pistil  or  gynoecium. 

Perigynous,  inserted  on  the  calyx,  that  is, 
with  the  lower  part  of  filament  adnate  to  the 
calyx  tube. 

Epigynous,  borne  apparently  on  the  top  of  the 
ovary;  all  which  is  shown  in  Figs.  182-186. 

Gynandrous  is  another  term  relating  to  inser-    207.  Style  of  a  Lady's 
tion  of  rarer  occurrence,  that  is,  where  the  sta- 
mens are  inserted  on  (in  other  words,  adnate  to) 
the  style,  as  in  Lady's  Slipper  (Fig.  207),  and  in 
the  Orchis  family  generally. 

271.  In  relation  to  each  other,  stamens  are 
more  commonly 

Distinct,  that  is,  without  any  union  with  each 
other.  But  when  united,  the  following  tech- 
nical terms  of  long  use  indicate  their  modes  of 
mutual  connection  :  — 

Monadelphous  (from  two  Greek  words,  mean- 


Slipper  Cypri- 
pedium) ,  and 
stamens  united 
with  it;  a,  a, 
the  anthers  of 
the  two  good 
stamens ;  st,  an 
abortive  sta- 
men, what 
should  be  its 
anther  changed 
into  a  petal-like 
body;  stig,  the 
stigma. 


THE  FLOWER 


135 


208 


210 


ing  "in  one  brotherhood  "),  when  united  by  their  filaments  into  one 
set,  usually  into  a  ring  or  cup  below,  or  into  a  tube,  as  in  the  Mallow 
family  (Fig.  208),  the  Passion  Flower  (Fig.  202),  and  the  Lupine 
(Fig.  210). 

Diadelphous  (meaning  in  two  brother- 
hoods), when  united  by  the  filaments  into 
two  sets,  as  in  the  Pea  and  most  of  its  near 
relatives  (Fig.  209),  usually  nine  in  one  set, 
and  one  in  the  other. 

Triadelplwus  (three  brotherhoods),  when 
the  filaments  are  united  in  three  sets  or 
clusters,  as  in  most  species  of  Hypericum. 

Pentad elplious  (five  brotherhoods),  when  in  five  sets,  as  in  some 
species  of  Hypericum  and  in  American  Linden. 

Polyadelphous  (many  or  several  brotherhoods)  is  the  term  generally 
employed  when  these  sets  are  several,  or  even  more  than  two,  and  the 
particular  number  is  left  unspecified.  These  terms  all  relate  to  the 
filaments. 

Syngenesious  is  the  term  to  denote  that  stamens  have  their  anthers 
united,  coalescent  into  a  ring  or  tube ;  as  in  Lobelia,  in  Violets,  and 
in  all  of  the  great  family  of  Composites  (Fig.  211). 

272.  Their  number  in  a  flower  is  commonly  expressed  directly,  but 
sometimes  adjectivelyyJ>y  a  series  of  terms  which  were  the  names  of 
classes  in  the  Linnsean  artificial  system,  of  which  the  following  names, 

as  also  the  preceding,  are  a  survival :  — 

ij  Monandrous,  i.e.  solitary-stamened,  when  the  flower  has  only 

one  stamen, 

Diandrous,  when  it  has  two  stamens  only, 
Triandrous,  when  it  has  three  stamens;  and  so  on. 
Didynamous,  when,  being  only  four,  they  form  two  pairs, 
one  pair  longer  than  the  other,  as  in  the  Trumpet  Creeper, 
in  Gerardia,  etc. 

Tetradynamous,  when,  being  only  six,  four  of  them  surpass  the  other 
two,  as  in  the  Mustard  flower  and  most  of  the  Cruciferous  Family 
(Fig.  179). 

273.  The  Anther  is  said  to  be 

Innate  (as  in  Fig.  212),  when  it  is  attached 
by  its  base  to  the  very  apex  of  the  filament, 
turning  neither  inward  nor  outward; 

Adnate  (as  in  Fig.  213),  when  attached  as 
it  were  by  one  face,  usually  for  its  whole  length, 
to  the  side  of  a  continuation  of  the  filament;  and 

Versatile  (as  in  Fig.  214),  when  fixed  by  or 
near  its  middle  only  to  the  very  point  of  the  filament,  so  as  to  swing 
loosely,  as  in  the  Lily,  in  Grasses,  etc.    Versatile  or  adnate  anthers  are 


I 

211 


213        214 


136 


THE  FLOWER 


215    216    217 


Introrse,  or  incumbent,  when   facing  inward,  that   is,  toward    the 
center  of  the  flower,  as  in  Magnolia,  Water  Lily, 

efcc- 

Extrorse,   when    facing    outward,    as    in    the 
Tulip  Tree. 

274.  Anthers  may  become  one-celled  either  by 
confluence  or  by  suppression. 

275.  By  confluence,  when    the  two  cells  run 
together   into  one,  as   they   nearly   do   in   most 

species  of  Pentstemon  (Fig.  216),  more  so  in   Monarda  (Fig.  219), 
and  completely  in  the  Mallow  (Fig.  217)  and  all  the  Mallow  family. 

276.  By  suppression  in  certain  cases  the  anther  may  be  reduced  to 
one  cell  or  halved.  In  Globe  Amaranth  (Fig.  218)  there  is  a 
single  cell  without  vestige  of  any  other.  Different  species 
of  Sage  and  of  the  White  Sages  of  California  show  various 
grades  of  abortion  of  one  of  the  anther  cells,  along  with  a 
singular  lengthening  of  the  connective  (Figs.  220-224). 


224  225  226 

225,  226.  Pollinia :  225,  a  pair  of  pollinia  of  a  Milkweed  (Asclepias)  attached 
by  stalks  to  a  gland;  moderately  magnified;  22(5,  pollinium  of  an 
Orchis  (Habenaria),  with  its  stalk  attached  to  a  sticky  gland,  mag- 
nified ;  each  of  the  packets  or  partial  pollinia  of  which  it  is  made  up 
is  composed  of  a  large  number  of  pollen  grains. 

Pollinia.  —  In  Milkweeds  and  in  most  Orchids  all  the  pollen  of  an 
anther  cell  is  compacted  or  coherent  into  one  mass,  called  a  pollen 
mass,  or  POLLINIUM,  plural  POLLINIA  (Figs.  225,  226). 


The  Ovule 

277.  Ovule  (from  the  Latin,  meaning  a  little  egg)  is  the  technical 
name  of  that  which  in  the  flower  answers  to  and  becomes  the  seed. 

278.  Ovules  are  naked  in   gymnospermous  plants  (as  above  de- 
scribed) ;  in  all  others  they  are  inclosed  in  the  ovary.     They  may  be 
produced  along  the  whole  length  of  the  cell  or  cells  of  the  ovary,  and 
then  they  are  apt  to  be  numerous ;  or  only  from  some  part  of  it,  gen- 
erally the  top  or  the  bottom.     In  this  case  they  are  usually  few  or 
single  (solitary,  as  in  Figs.  228-230).    They  may  be  sessile,  i.e.  without 


THE  FLOWER 


137 


stalk,  or  they  may  be  attached  by  a  distinct  stalk,  the  FUNICLE  or 
FUNICULUS  (Fig.  227). 


22T  228 

227-230.  Ovules:  227,  a  cluster  of  ovules,  pendulous  on  their  funicles;  228, 
section  of  the  ovary  ^f  a  Buttercup,  lengthwise,  showing  its  ascending 
ovule  ;  229,  section  of  the  ovary  of  Buckwheat,  showing  the  erect  ovule ; 
230,  section  of  the  ovary  of  Anemone,  showing  its  suspended  ovule. 

279.  In  structure  an  ovule  is  a  pulpy  mass  of  tissue,  usually  with 
one  or  two  coats  or  coverings.     The  following  parts  are  to  be  noted; 
viz. :  — 

KERNEL  or  NUCELLUS,  the  body  of  the 
ovule.  In  the  Mistletoe  and  some  related 
plants,  there  is  only  this  nucellus,  the  coats 
being  wanting. 

TEGUMENTS,  or  coats,  sometimes  only  one, 
more  commonly  two,  an  outer  and  an  inner 

one'  231.  Longitudinal  section  of 

ORIFICE,     or     FORAMEN,     an     opening  an  ovule  enlarged, 

through  the  coats  at  the  organic  apex  of  the 

ovule.     In  the  seed  it  is  micropyle. 

CHALAZA,  the  place  where  the  coats  and 

the  kernel  of  the  ovule  blend. 

HILUM,  the  place  of  junction  of  the  funiculus  with  the  body  of  the 

ovule. 

280.  The  Kinds  of  Ovules.  —  The  ovules  in  their  growth  develop  in 
three  or  four  different  ways,  and  thereby  are  distinguished  into 


showing  the  parts: 
a,  outer  coat;  6, 
inner  coat;  c,  nu- 
cellus ;  d,  raphe. 


232-235.  Ovules:  232,  orthotropous  ovule  of  Buckwheat:  c,  hilum  and  cha- 
laza;  /,  orifice;  233,  campylotropous  ovule  of  a  Chickweed :  c,  hilum 
and  chalaza ;  /,  orifice;  234,  amphitropous  ovule  of  Mallow :  f,  orifice  ; 
h,  hilum  ;  r,  raphe;  c,  chalaza;  235,  anatropous  ovule  of  a  Violet;  the 
parts  lettered  as  in  the  last. 

Orthotropous,  or  straight,  those  which  develop  without  curving  or 
turning,  as  in  Fig.  232.     The  chalaza  is  at  the  insertion  or  base ;  the 


138  THE  FLOWER 

foramen  or  orifice  is  at  the  apex.  This  is  the  simplest,  but  the  least 
common,  kind  of  ovule. 

Campylotropous,  or  incurved,  in  which,  by  the  greater  growth  of  one 
side,  the  ovule  curves  into  a  kidney-shaped  outline,  so  bringing'  the 
orifice  down  close  to  the  base  or  chalaza ;  as  in  Fig.  233. 

Amphitropous,  or  half-inverted,  Fig.  234.  Here  the  forming  ovule, 
instead  of  curving  perceptibly,  keeps  its  axis  nearly  straight,  and,  as 
it  grows,  turns  round  upon  its  base  so  far  as  to  become  transverse  to 
its  funiculus,  and  adnate  to  its  upper  part  for  some  distance.  There- 
fore in  this  case  the  attachment  of  the  funiculus  or  stalk  is  about  the 
middle,  the  chalaza  is  at  one  end,  the  orifice  at  the  other. 

Anatropous,  or  inverted,  as  in  Fig.  235,  the  commonest  kind,  so 
called  because  in  its  growth  it  has  as  it  were  turned  over  upon  its 
stalk,  to  which  it  has  continued  adnate,  the  attached  portions  o£  the 
stalk  being  known  as  the  raphe.  The  organic  base,  or  chalaza,  thus 
becomes  the  apparent  summit. 

Arrangement  of  Parts  in  the  Bud 

281.  Estivation  was  the  fanciful  name  given  by  Linnaeus  to  denote 
the  disposition  of  the  parts,  especially  the  leaves  of  the  flower,  before 
anthesis,  i.e.  before  the  blossom  opens.  Prcefloration,  a  better  term,  is 
sometimes  used.  This  is  of  importance  in  distinguishing  different 
families  or  genera  of  plants,  being  generally  uniform  in  each.  The 
aestivation  is  best  seen  by  making  a  cut  across  the  flower  bud  ;  and 
it  may  be  expressed  in  diagrams,  as  in  the  accompanying  figures. 


ff 

y 


240 


282-  The  pieces  of  the  calyx  or  the  corolla  either  overlap  each 
other  in  the  bud,  or  they  do  not.  When  they  do  not  overlap,  the 
aestivation  is 

Valvate,  when  the  pieces  meet  each  other  by  their  abrupt  edges, 
without  any  infolding  or  overlapping,  as  in  the  calyx  of  the  Linden  or 
Basswood  (Fig.  236). 

Induplicate,  which  is  valvate  with  the  margins  of  each  piece  project- 
ing inwards,  as  in  the  calyx  of  a  common  Virgin's-bower  (Fig.  238),  or 

Involute,  which  is  the  same,  but  with  the  margins  rolled  inward, 
as  in  most  of  the  large-flowered  species  of  Clematis  (Fig.  239). 

Reduplicate,  a  rarer  modification  of  valvate,  is  similar,  but  with 
margins  projecting  outward. 

Open,  the  parts  not  touching  in  the  bud,  as  the  calyx  of  Mignonette. 


THE   FLOWER  139 

283.  When  the  pieces  overlap  in  the  bud,  it  is  in  one  of  two  ways ; 
either  every  piece  has  one  edge  in  and  one  edge  out,  or  some  pieces 
are  wholly  outside  and  others  wholly  inside.     In  the  first  case  the 
aestivation  is 

Convolute,  also  named  contorted  or  twisted,  as  in  Fig.  240,  a  cross 
section  of  a  corolla  very  strongly  thus  convolute  or  rolled  up  to- 
gether. Here  one  edge  of  every  petal  covers  the  next  before  it,  while 
its  other  edge  is  covered  by  the  next  behind  it.  The  other  mode 
is  the 

Imbricate,  or  imbricated,  in  which  the  outer  parts  cover  or  overlap 
the  inner  so  as  to  "break  joints,"  like  tiles  or  shingles  on  a  roof; 
whence  the  name  (calyx  in  Fig.  237). 

284.  The  imbricate  and  the  convolute  modes  sometimes  vary  one 
into  the  other,  especially  in  the  corolla. 

285.  In  a  gamopetalous  corolla  or  gamosepalous  calyx,  the  shape 
of  the  tube  in  the  bud  may  sometimes  be  noticeable.     It  may  be 

Plicate,  or  plaited,  that  is,  folded  lengthwise;  and  the  plaits  may 
either  be  turned  outward,  forming  projecting  ridges,  as  in  the 
corolla  of  Campanula;  or  turned  inward,  as  in  that  of  Gentian 
or  of  Belladonna. 

Position  and  Arrangement  of  Flowers,  or  Inflorescence 

286.  Inflorescence,  which  is  the  name  used  by  Linnaeus  to  sig- 
nify mode  of  flower  arrangement,  is  of  three  classes ;  namely,  inde- 
terminate, when  the  flowers  are  in  the  axils  of  the  leaves,  that  is, 
are  from  axillary  buds ;    determinate,  when   they  are   from  terminal 
buds,  and  so  terminate  a  stem  or  branch ;    and  mixed,  when  these  two 
are  combined. 

287.  Indeterminate,   or  indefinite, 
Inflorescence  is  so  named  because,  as 
the  flowers  all  come  from  axillary  buds, 
the  terminal  bud  may  keep  011  grow- 
ing and  prolong  the  stein  indefinitely. 
This  is  so  in  Moneywort  (Fig.  241). 

288.  When  flowers  thus  arise  singly  from  the  axils  of  ordinary 
leaves,  they  are  axillary  and  solitary,  not  collected  into  flower  clusters. 

289.  But  when  several  or  many  flowers  are  produced  near  each 
other,  the  accompanying  leaves  are  apt  to  be  of  smaller  size,  or  of 
different  shape  or  character:  then  they  are  called  BRACTS,  and  the 
flowers  thus  brought  together  form  a  cluster.     The  kinds  of  flower 
clusters  of  the  indeterminate  class  have  received  distinct  names,  ac- 
cording to  their  form  and  disposition.      They  are  principally  raceme, 
corymb,  umbel,  spike,  head,  spadix,  catkin,  and  panicle. 

290.  In  defining  these  it  will  be  necessary  to  use  some  of  the  fol- 
lowing terms  of  descriptive  botany  which  relate  to  inflorescence.     If  a 


140  THE  FLOWER 

flower  is  stalkless,  i.e.  sits  directly  in  the  axil  or  other  support,  it  is  said 
to  be  sessile.  If  raised  on  a  naked  stalk  of  its  own  (as  in  Fig.  241),  it 
is  pedunculate,  and  the  stalk  is  a  PEDUNCLE. 

291.  A  peduncle  on  which  a  flower  cluster  is  raised  is  a  common 
peduncle.     That  which  supports  each  separate  flower  of  the  cluster  is  a 
partial  peduncle,  and  is  generally  called  the  PEDICEL.     The  portion 
of  the  general  stalk  along  which  flowers  are  disposed  is  called  the 
axis  of  inflorescence,  or,  when  covered  with  sessile  flowers,  the  rachis 
(backbone),  and  sometimes  the  receptacle.      The  leaves  of   a  flower 
cluster  generally  are  termed  BRACTS.     But  when  bracts  of  different 
orders  are  to  be  distinguished,  those  on  the  common  peduncle  or  axis, 
and  with  a  flower  in  their  axil,  keep  the  name  of  bracts ;  and  those 
on  the  pedicels  or  partial  flower  stalks,  if  any,  that  of  BRACTLETS. 

292.  A  Raceme    (Fig.  242)  is  that  form  of  flower  cluster  in  which 
the  flowers,  each  on  its  own  foot  stalk  or  pedicel,  are  arranged  along 
the  sides  of  a  common  stalk  or  axis  of  inflorescence ;  as  in  the  Lily 

of  the  Valley,  Currant, 
Barberry,  one  section  of 
Cherry,  etc.  Each  flower 
comes  from  the  axil  of  a 
small  leaf,  or  bract,  which, 
however,  is  often  so  small 
that  it  might  escape  notice, 
242^  243  244  and  even  sometimes  (as  in 

the  Mustard  family)  dis- 
appears altogether.  The  lowest  blossoms  of  a  raceme  are  of  course 
the  oldest,  and  therefore  open  first,  and  the  order  of  blossoming  is 
ascending.  The  summit  never  being  stopped  by  a  terminal  flower, 
may  go  on  to  grow,  and  often  does  so  (as  in  the  common  Shep- 
herd's Purse),  producing  lateral  flowers  one  after  another  for  many 
weeks. 

293.  A  Corymb  (Fig.  243)  is  the  same  as  a  raceme,  except  that  it 
is  flat  and  broad,  either  convex,  or  level-topped.     ThaJ  is,  a  raceme 
becomes  a  corymb  by  lengthening  the  lower  pedicels,  while  the  upper- 
most remain  shorter.     The  axis  of  a  corymb  is  short  in  proportion  to 
the  lower  pedicels.     By  extreme  shortening  of  the  axis  the  corymb 
may  be  converted  into 

294.  An  Umbel  (Fig.  244),  as  in  the  Milkweed,  a  sort  of  flower 
cluster  where  the  pedicels  all  spring  apparently  from  the  same  point, 
from  the  top  of  the  peduncle,  so  as  to  resemble,  when  spreading,  the 
rays  of  an  umbrella ;  whence  the  name.    Here  the  pedicels  are  oome- 
times  called  the  rays  of  the  umbel.     And  the  bracts,  when  brought 
in  this  way  into  a  cluster  or  circle,  form  what  is  called  an  INVOLUCRE. 

295.  The  corymb  and  the  umbel  being  more  or  less  level-topped, 
bringing  the  flowers  into  a  horizontal  plane  or  a  convex  form,  the 


THE  FLO  WEE 


141 


ascending  order  of  development  appears  as  centripetal.  That  is,  the 
flowering  proceeds  from  the  margin  or  circumference  regularly  toward 
the  center;  the  lower  flowers  of  the  former  answering  to  the  outer 
ones  of  the  latter. 

296.  In  these  three  kinds  of  flower  clusters,  the  flowers 
are  raised  on  conspicuous  pedicels  or  stalks  of  their  own. 
The  shortening  of  these  pedicels,  so  as  to  render  the  flowers 
sessile  or  nearly  so,  converts  a  raceme  into  a  spike,  and  a 
corymb  or  an  umbel  into  a  head. 

297.  A  Spike  is   a  flower  cluster  with  a  more  or   less 
lengthened  axis,  along  which  the  flowers  are  sessile  or  nearly 
so ;  as  in  the  Plantain  (Fig.  245). 

298.  A  Head  is  a  round  or  round- 
ish cluster  of  flowers,  which  are  sessile 
on  a  very  short  axis  or  receptacle,  as 
in  the  Buttonball,  Buttonbush  (Fig. 
246),  and  Red  Clover.  It  is  just  what  a  spike 
would  become  if  its  axis  were  shortened ;  or  an 
umbel,  if  its  pedicels  were  all  shortened  until 
the  flowers  became  sessile.  The  head  of  the 
Buttonbush  is  naked;  but  that  of  the  Thistle, 
of  the  Dandelion,  and  the  like,  is  surrounded 
by  empty  bracts,  which  form  an  involucre.  Two 

particular  forms  of  the  spike  and  the  head  have  received  particular 

names  ;  namely,  the  spadix  and  the  catkin. 

299.  A  Spadix  is  a  fleshy  spike  or  head,  with  small 
and  often  imperfect  flowers,  as  in  the  Calla,  Indian  Tur- 
nip (Fig.  173),  Sweet  Flag,  etc.     It  is  commonly  sur- 
rounded  or   embraced    by   a   peculiar   enveloping  leaf, 
called  a  SPATHE. 

300.  A  Catkin,  or  ament,  is  the  name  given  to  the 
scaly  sort  of  spike  of  the  Birch  (Fig.  247)  and  Alder, 
the  Willow  and  Poplar,  and  one  sort  of  flower  clusters 
of  the  Oak,  Hickory,  and  the  like, — the  so-called  amen- 
taceous trees. 

301.    Compound  flower  clusters 
of  these  kinds  are  not  uncommon. 
When    the    stalks   which    in    the 
simple  umbel  are  the  pedicels  of 
single  flowers  themselves  branch  into  an  umbel, 
a  compound  umbel  is  formed.     This  is  the  inflor- 
escence of   Caraway  (Fig.  248),  Parsnip,  and 

almost  all  of  the   great  family  of    umbelliferous    (umbel-bearing) 

plants. 

The    secondary    or   partial    umbels    of    a  compound    umbpl     are 


Jf 


247 


248 


142 


THE  FLOWER 


UMBELLETS.     When  the   umbellets  are  subtended  by  an  involucre, 
this  secondary  involucre  is  called  an  INVOLUCEL. 

302.    A  compound  raceme  is  a  cluster  of  racemes  racemosely  ar- 
ranged, as  in  Smilacina  racemosa.     A  compound  corymb  is  a  corymb, 
some  branches  of  which  branch  again  in  the  same  way, 
as  in  Mountain  Ash.     A  compound  spike  is  a  spicately 
disposed  cluster  of  spikes. 

303.  A  Panicle,  such   as  that  of    Oats   and   many 
Grasses,  is  a  compound  flower  cluster  of  a  more  or  less 
open  sort  which  branches  with  apparent  irregularity, 
neither  into  corymbs  nor  racemes.     Figure  249  repre- 
sents the  simplest  panicle.     It  is,  as  it  were,  a  raceme 
of  which  some  of  the  pedicels  have  branched 'so  as  to 
bear  a  few  flowers   on   pedicels  of  their  own,  while 
others  remain  simple.     A  compound  panicle  is  one  that 
branches  in  this  way  again  and  again. 

304.  Determinate  Inflorescence  is  that  in  which  the 
flowers  are  from  terminal  buds.     The  simplest  case  is 
that  of  a  solitary  terminal  flower,  as  in  Fig.  250.     This 
stops  the  growth  of  the  stem;   for  its  terminal  bud, 

becoming  a  blossom,  can  no  more  lengthen  in  the  manner  of  a  leaf 
bud.  Any  further  growth  must  be  from  axillary  buds  developing 
into  branches.  If  such  branches  are  leafy  shoots,  at  length  terminated 
by  single  blossoms,  the  inflorescence  still  consists  of  solitary  flowers  at 
the  summit  of  stern  and  branches.  But  if  the  flowering  branches 
bear  only  bracts  in  place  of  ordinary  leaves,  the  result  is  the  kind  of 
flower  cluster  called 

305.  A  Cyme.  —  This  is  commonly  a  flat-topped  or  convex  flower 
cluster,  like  a  corymb,  except  that  the  blossoms  are  from  terminal 
buds.  Figure  251  illustrates  the  simplest  cyme  in  a  plant  with  opposite 
leaves ;  namely,  with  three  flowers.  The  middle  flower,  a,  terminates 
the  stem ;  the  two  others,  bb,  terminate  branches,  one  from  the  axil 
of  each  of  the  uppermost  ft  a  6 

leaves;  and  being  later  than 
the  middle  one,  the  flowering 
proceeds  from  the  center  out- 
ward, or  is  centrifugal.  This 
is  the  opposite  of  the  indeter- 
minate mode,  or  that  where  all 
the  flower  buds  are  axillary. 
If  flowering  branches  appear  from  the  axils  below,  the  lower  ones  are 
the  later,  so  that  the  order  of  blossoming  continues  centrifugal  or, 
which  is  the  same  thing,  descending,  as  in  Fig.  253,  making  a  sort 
of  reversed  raceme  or  false  raceme,  —  a  kind  of  cluster  which  is  to 
the  true  raceme  Just  what  the  flat  cyme  is  to  the  corymb. 


251 


252 


THE   FLOWER 


143 


f 


253.  Diagram  of  a 
simple  cyme 
in  which  the 
axis  length- 
ens, so  as-  to 
take  the  form 
of  a  raceme. 


306.  Wherever  there  are  bracts  or  leaves,  buds  may  be  produced 
from  their  axils  and  appear  as  flowers.     Figure  252  represents  the  case 
where  the  branches,  bb,  of  Fig.  251,  each  with  a  pair  of  small  leaves 
or  bracts  about  their  middle,  have  branched  again,  and  produced  the 
branchlets  and  flowers,  cc,  on  each  side.    It  is  the  continued  repetition 
of  this  which  forms  the  full  or  compound  cyme, 

such  as  that  of  the  Hobblebush,  Dogwood,  and 
Hydrangea. 

307.  A  Fascicle  (meaning  a  bundle),  like  that 
of  the  Sweet  William  and  Lychnis  of  the  gardens, 
is  only  a  cyme  with  the  flowers  much  crowded 
together. 

308.  A  Glomerule  is  a  cyme   still  more  com- 
pacted, so  as  to  imitate  a  head.     It  may  be  known 
from  a  true  head  by  the  flowers  not  expanding 
centripetally ;  that  is,  not  from  the  circumference 
toward  the  center. 

309.  Scorpioid  or  Helicoid  Cymes,  of  various 
sorts,  are  forms  of  determinate  inflorescence  (often 
puzzling  to  the  student)  in  which  one-half  of  the 
ramification  fails  to  appear.     So  that  they  may 
be  called  incomplete  cymes.     The  commoner  forms 

may  be  understood  by  comparing  a  complete  cyme,  like  that  of 
Fig.  252,  with  Fig.  254,  the  diagram  of  a  cyme  of  an  opposite-leaved 
plant,  having  a  series  of  terminal  flowers 
and  the  axis  continued  by  the  development 
of  a  branch  in  the  axil  of  only  one  of  the 
leaves  at  each  node.  The  dotted  lines  on 
the  left  indicate  the  place  of  the  wanting 
branches,  which  if  present  would  convert 
this  scorpioid  cyme  into  the  complete  one 
of  Fig.  252.  Figure  254  a  is  a  diagram 
of  similar  inflorescence  with  alternate 
leaves.  An  axis  made  up  in  this  way  of  a 
succession  of  branches  is  termed  a  sympodium. 

310.  Mixed  Inflorescence  is  that  in  which  the  two  plans  are  mixed 
or  combined  in  compound  clusters.     A  mixed  panicle  is  one  in  which, 
while  the   primary  ramification  is  of   the   indeterminate  order,  the 
secondary  or  ultimate  is  wholly  or  partly  of  the  determinate  order.     A 
contracted  or  elongated  inflorescence  of  this  sort  is  called  a  THYRSUS. 
Lilac  and  Horse-chestnut  afford  common  examples  of  mixed  inflores- 
cence of  this  sort.     When  loose  and  open  such  flower  clusters  are  called 
oy  the  general  name  of  panicles.     The  heads  of  Composite  are  cen- 
tripetal;    but  the  branches  or  peduncles  which  bear  the  heads  are 
usually  of  centrifugal  order. 


254  a 


144  LABORATORY  STUDIES   OF  THE  FRUIT 

XIII.    LABORATORY  STUDIES   OF   THE  FRUIT 

The  whole  purpose  of  the  fruit  is  embodied  in  the  seed. 
The  portion  external  to  the  seed  is  important  in  the  life 
history  of  the  plant  only  as  it  ministers  to  the  maturing, 
preservation,  transporting,  or  planting  of  the  germ.  The 
ways  in  which  the  character  of  the  exterior  parts  of  the 
fruit  affects  the  destiny  of  the  seed  will  be  studied  after 
the  general  structure  of  fruits  has  been  examined. 

The  studies  of  the  first  Exercise  have  to  do  with  the 
parts  of  the  fruit  external  to  the  seed  ;  the  second 
Exercise  is  concerned  with  the  seed  itself  ;  and  the  third, 
with  dissemination. 

EXERCISE  XXXV.     FLORAL  ORGANS  INVOLVED  IN  THE  FRUIT 

Wild  Indigo. —  Notice  the  base  and  the  slender  termination  of  the 
pod.  What  was  this  termination  in  the  flower  ?  What  .still  surrounds 
the  pod  stalk?  Can  you  discover  any  marks  of  other  organs,  now 
fallen  away  ?  Open  the  pod :  where  are  the  seeds  attached  ?  Pod  and 
seeds  are  the  ripened  forms  of  what  members  of  the  flower?  How 
many  carpels  in  this  fruit  ?  The  ripened  ovary  is  termed  the  pericarp. 

Violet.  —  After  examining  all  exterior  features,  cut  a  cross  section. 
With  the  lens,  and  by  trying  the  seeds  with  a  needle,  find  the  places 
of  attachment.  How  many  placentae,  f  Of  how  many  carpels  is  the 
pod  composed?  From  dried  and  opened  specimen0  determine  whether 
the  pod  bursts  between  the  carpels  or  along  the  carpellary  midribs. 
Of  what  floral  organ  does  the  fruit  consist  ? 

Cranberry.  —  Opposite  the  stem  end  is  a  slight  hollow,  roughly 
square,  edged  and  often  nearly  covered  in  by  four  projections.  Cut 
these  projections  away.  Observe  the  bottom  of  the  depression.  At 
the  center  is  a  single  scar,  marking  the  position  of  what  member  of 
the  flower  ?  Around  this,  within  the  crater,  notice  two  circles  of  scars. 
What  are  they  ?  Finally,  what  is  the  nature  of  the  four  projections 
first  noticed  and  then  cut  away?  Parts  of  what  organs  of  the  original 
flower  now  compose  the  berry? 

Cut  the  fruit  transversely.  How  many  carpels  compose  it?  The 
size  of  the  cavities  in  which  the  seeds  lie  is  striking  when  compared 
with  the  minute  size  of  the  seeds  themselves.  Will  the  berry  float? 
Try  it.  Count  and  record  the  number  of  seeds. 

Draw  :  Wild  Indigo.  The  pod,  with  persistent  calyx.  This  sort  of 
fruit  is  termed  a  legume. 

Violet.  Cross  section,  to  show  the  seeds  attached  (  x  5).  The 
dehiscent  fruit  (  x  2).  The  fruit  is  termed  a  capsule. 


LABORATORY  STUDIES   OF  THE  FRUIT  145 

Cranberry.  Cross  section,  showing  cavities  and  attachment  of  seeds 
(x  2).  The  terminal  depression  showing  remains  of  the  flowers 
(  x  10).  Soft,  fleshy  fruits  of  this  sort  are  termed  berries. 

Checkerberry. — Dissect  the  fruit.  What  is  the  morphological 
nature  of  the  lower,  fleshy  part  ? 

Draw  a  longitudinal  section  to  show  all  parts  —  including  the  seeds 
in  one  of  the  cavities  —  and  their  arrangement  (x  3). 

The  Rose  hip.  —  Examine  the  fruit  to  discover,  if  possible,  where 
the  floral  parts  were  situated.  Cut  the  hip  open.  Are  seeds  seen? 
Are  seeds  of  Angiosperms  produced  in  an  open  receptacle  or  cavity,  as 
these  seedlike  bodies  are?  Are  they  seeds  or  fruits?  The  hollow, 
pulpy  portion  bearing  them  on  its  inner  surface  is  an  enlarged 
receptacle. 

Draw  a  diagram  representing  a  longitudinal  section  (  x  2-3). 

EXERCISE  XXXVI.     THE  SEED 

The  student  is  already  familiar  with  the  interior  of  the  seed  —  with 
embryo  and  albumen.  The  integuments  need  to  be  looked  at  more 
particularly  than  has  been  done  heretofore. 

Squash.  —  Notice  the  place  at  which  the  seed  was  broken  from  its 
connection  with  the  placenta.  It  is  called  the  hilum.  Beside  this  there 
is  a  distinct  aperture  leading  into  the  interior,  the  micropyle.  Cut 
away  the  shell.  How  many  seed  coats?  This  is  the  characteristic 
number.  The  outer  is  the  testa;  the  inner,  the  tegmen. 

Draw  a  cross  section  of  the  Squash  seed  (diagrammatic). 

Castor  Bean.  —  On  one  side  observe  a  straight,  dark  line,  running 
three  quarters  the  length  of  the  seed  (the  raplie).  At  one  end  is  a 
very  slight  elevation,  the  point  at  which  the  coats  are  organically 
connected  with  the  kernel ;  this  point  is  the  chalaza.  At  the  other 
end  is  the  hilum,  nearly  covered  by  a  structure  called  the  caruncle. 

Bean. —  At  one  side  of  the  hilum  is  the  micropyle,  more  easily  made 
out  if  the  material  has  been  properly  soaked.  On  the  other  side  of 
the  hilum,  running  to  the  end  of  the  bean,  is  a  ridge,  more  or  less 
indistinct  —  the  raphe.  Overlying  its  inner  extremity,  next  the  hilum, 
is  a  heart-shaped,  purple  excrescence,  called  the  strophiole. 

Draw  the   bean,  showing   the   features    indicated  ( x  3). 

Outgrowths  of  the  testa.  —  By  the  aid  of  the  hand  lens  make 
enlarged  drawings  of  the  seeds  of  Milkweed  and  of  the  Trumpet 
Creeper.  Cut  the  seed  of  the  Cotton  Plant  in  half.  Draw  the 
section,  so  as  to  show  the  length  of  the  Cotton  fibers  relatively  to  the 
diameter  of  the  seed  proper.  What  is  the  use  of  these  outgrowths  ? 

EXERCISE  XXXV1T.     THE  FRUIT  IN  RELATION  TO  DISSEMINATION 

The  need  of  dissemination  will  be  most  keenly  realized  by  a  rough 
computation  of  the  number  of  seeds  produced  by  a  single  plant,  all 
OUT.  or  ROT.  — 10 


146  LABORATORY  STUDIES   OF  THE  FRUIT 

of  which  would  have  a  chance  of  germinating  upon  the  plot  of  ground 
occupied  by  the  parent,  unless  carried  elsewhere.  Take  as  an  example 
the  Cranberry,  studied  in  Exercise  XXXV.  Allow  fifty  berries  to  a 
single  bush,  and  multiply  by  the  number  of  seeds  actually  observed 
in  one  berry.  The  resulting  product  represents  the  possible  number 
of  seedlings  upon  less  than  a  square  yard  of  ground. 

That  even  one  seedling  should  occupy  part  of  the  soil  held  by  the 
parent  plant  would  evidently  be  disadvantageous  to  both.  Accord- 
ingly, plants  exhibit  a  great  variety  of  devices  by  which  the  service 
of  various  agencies  is  secured  for  the  dispersal  of  the  seeds.  The 
means  of  dissemination  may  be  (1)  some  feature  of  the  coat  of  the 
seed  itself,  (2)  some  special  character,  construction,  or  outgrowth  of 
the  pericarp.  The  first  case  has  been  seen  in  the  Milkweed;  the 
second  remains  to  be  studied  in  more-  detail. 

Bladder  Nut.  —  Examine  the  bladdery  fruit  before  dehiscence,  not- 
ing (1)  the  morphology  of  the  pericarp,  (2)  the  number  of  carpels, 
and  (3)  the  relative  size  of  the  pericarp  and  the  seeds.  Place  the 
fruit  on  the  table.  Blow  it  about.  The  object  of  the  inflated  peri- 
carp becomes  apparent. 

Draw  the  fruit,  natural  size.  Indicate  in  dotted  line  the  position 
and  size  of  the  seed. 

Curled  Dock.  —  With  a  lens  examine  the  three-winged  and  coarsely 
veined  parts,  each  bearing  at  its  base  a  granule  resembling  a  seed. 
They  are  persistent  sepals,  and  are  closely  appressed.  Hidden  between 
them  is  the  three-angled  achene  (dry  pericarp,  containing  a  single 
seed).  The  dispersal  apparatus  here  comes  from  the  calyx.  Note 
how  readily  the  fruit  is  driven  by  a  mere  breath. 

Draw  the  fruit,  with  one  sepal  removed  to  show  achene,  magnified 
about  eight  diameters. 

Bur  Marigold.  —  The  barbed  bristles,  well  seen  with  the  lens,  are 
morphologically  the  border  of  the  calyx,  the  lower  part  of  which  is 
adherent  to  the  pericarp.  What  is  the  mode  of  dissemination  ? 

Draw  the  fruit,  magnified  about  four  diameters. 

Witch-hazel.  —  Notice  :  — 

(1)  The  pericarp  proper,  with  the  old  calyx  surrounding  the  lower 
half.  (2)  The  partial  splitting  at  the  tips  of  unopened  fruits.  (3)  The 
number  of  cells  (loculi)  in  the  opened  capsules.  (4)  The  mode  of 
dehiscence.  The  loculi  are  split  open  along  the  median  line  in  each 
case.  This  is  locnllcidal  dehiscence.  (5)  The  backward  curving  of  the 
open  jaws.  (6)  The  very  hard,  smooth  inner  surface  of  the  loculi,  and 
the  similar  surface  of  the  seeds,  which  indeed  makes  it  rather  difficult 
to  hold  them  securely  between  finger  and  thumb.  (7)  Cut  away  the 
calyx  and  the  outer,  softer  layer  of  the  pericarp.  It  will  be  seen  that 
the  inner  and  immediate  receptacle  of  the  seeds  is  a  bony  and  rather 
thick-vailed  double  case.  There  was  originally  one  seed  in  each 


THE  FRUIT  147 

compartment.  (8)  The  halves  (valves)  of  the  seed  case  are  separated 
nearly  to  the  middle,  cohering  only  by  their  basal  portions.  (9)  The 
edges  of  the  inner,  bony  seed  cases  curve  in  somewhat,  as  if  com- 
pressed. (10)  Try  to  fit  the  seeds  back  into  the  cases.  Are  the  cases 
large  enough  to  cover  the  seeds  ? 

The  fruit  of  Witch-hazel  is  a  projectile  apparatus.  As  the  valves 
open  wider  and  wider,  in  the  process  of  drying,  the  seeds  are  squeezed 
more  and  more  by  the  shrinkage  of  the  bony  layer  and  the  incurving 
of  the  valve  edges.  At  a  certain  point,  the  intensity  and  direction  of 
pressure  become  such  that  the  seed  is  shot  out  with  much  force  — 
enough  force,  under  the  most  favorable  conditions,  to  carry  the  seed 
to  a  distance  of  forty  or  fifty  feet. 

Draw  whatever  is  necessary  to  illustrate  your  notes  on  this  fruit. 


XIV.    THE  FRUIT 

311.  Nature  of  the   fruit.  —  The  mature  ovary  is   the 
Fruit.     In  the  strictest  sense  the  fruit  is  the  seed  vessel, 
technically  named  the  PERICARP.     But  practically  it  may 
include  other  parts  organically  connected  with  the  peri- 
carp.    The  calyx  especially,  or  a  part  of  it,  is  often  in- 
corporated with  the  ovary,  so  as  to  be  indistinguishably 
a  portion  of  the  pericarp.     The  receptacle  forms,  along 
with  the  calyx,  the  whole  bulk  of  such  edible  fruits  as 
Apples  and  Pears.     The  receptacle  is  an  obvious  part  in 
Blackberries  (see  Fig.  256),  and  is  the  whole  edible  por- 
tion in  the  strawberry. 

312.  A  cluster  of  distinct  carpels  may,  also,  in  ripening, 
be  consolidated  or  compacted,  so  as  practically  to  be  taken 
for  one  fruit.     Such  are   Raspberries,   Blackberries,  etc. 
Moreover,  the  ripened  product  of  many  flowers  may  be 
compacted  or  grown  together  so  as  to  form  a  single  com- 
pound fruit. 

THE   KINDS   OF  FRUITS 

313.  In  respect  to  composition,  fruits  may  be  classified 
into 

Simple,  those  which  result  from  the  ripening  of  a  single 
pistil,  and  consist  only  of  the  matured  ovary,  either  by 
itself,  as  in  a  Peach  (Fig.  255),  or  with  the  receptacle  and 


148 


THE  FRUIT 


255.   Sectioii  of  a  Peach. 


calyx  tube  completely  incorporated  with  it,  as  in  the  Goose- 
berry and  Pear  (Fig.  259). 

Aggregate,  when  a  cluster  of  carpels  of  the  same  flower 
are  crowded  into  a  mass ;  as  in 
Raspberries  and  Blackberries  (Fig. 
256). 

Accessory,  when  the  surroundings 
or  supports  of  the  pistil  make  up 
a  part  of  the  mass.  In  an  accessory 
fruit  such  as  the  Strawberry  the  great 
mass  is  receptacle  (Fig.  156). 

Multiple  or  collective,  when  formed 

from  several  flowers  consolidated  into  one  mass,  of  which 

the  common  receptacle  or  axis  of 

inflorescence,    the     floral     enve- 
lopes, and  even  the  bracts,  etc., 

make  a  part.     A  Mulberry  (Fig. 

257,    which    superficially    much 

resembles    a    Blackberry)    is    of 

this  multiple  sort.     A  Pineapple 

is  another  example. 

Stone    fruits,     or     drupaceous 

(Fig.  255),  the  outer  part  fleshy 

like  a  berry,  the  inner  hard  or 

stony,  like  a  nut ;  and 

Dry  fruits    (Fig.    266),  those    257 

which  have  no  flesh  or  pulp. 

314.  In  reference  to  the  splitting  apart  of  the  pericarp 
for  the  liberation  of  the  seeds,  fruits  are  said  to  be 

Dehiscent,  when  they  open  regularly  along  certain  lines. 
A  dehiscent  fruit  almost  always  contains  many  or  several 
seeds,  or  at  least  more  than  one  seed  (Fig.  267). 

Indehiscent,  when  they  do  not  open  at  maturity.  Fleshy 
fruits  and  stone  fruits  are  of  course  indehiscent.  The 
seed  becomes  free  only  through  decay  or  by  being  fed 
upon  by  animals.  Of  dry  fruits  also  many  are  indehiscent. 

315.  The  principal  kinds  of  fruits  which  have  received 
distinctive  names  are  the  following  :  — 


257 

256.  Aggregate  fruit  of  the 
Blackberry :  consisting 
of  a  number  of  ripened 
pistils  crowded  on  a 
fleshy  receptacle.  At 
the  right,  one  of  the  in- 
dividual fruits  (a  drupe) 
further  enlarged. 
Multiple  fruit  of  the  Mul- 
berry. 


THE  FRUIT 


149 


258.   Fruit  of  the 
Cranberry. 


259. 


Sections  of 
Pear. 


316.  The  berry,  such  as  the  Gooseberry  and  Currant,  the  Blueberry 
and  Cranberry  (Fig.  258),  the  Tomato,  and  the  Grape. 

Here  the  whole  flesh  is  soft  throughout.    The  Orange 
is  a  berry  with  a  leathery  rind. 

317.  The  pome,  a  name  applied 
to  the  Apple,  Pear  (Fig.  259),  and 
Quince.      These   are   fleshy   fruits, 
like    a    berry,    but    the    principal 
thickness  is  the  enlarged  receptacle, 
only  the  papery  pods  arranged  like 
a  star  in  the  core  really  belonging 
to  the  carpels. 

318.  The  drupe,   or  stone  fruit, 
of  which   the   Cherry,   Plum,  and 
Peach  (Fig.  255)  are  familiar  exam- 
ples.   In  these  the  outer  part  of  the 
thickness  of  the  pericarp  becomes 

fleshy,  or  softens  like  a  berry,  while  the  inner  hardens  like  a  nut. 

Two  portions  of  the  drupe  are  thus  distinguishable,  named  respec- 
tively exocarp  —  the  outer,  fleshy  layer; 
and  the  endocarp  —  the  innermost  layer, 
the  stone. 

319~,  Of  dry  fruits  there  is  a  great 
diversity  of  kinds  having  distinct  names. 
320.  The  achene  is  a  small,  dry,  and 
indehiscent  one-seeded  fruit,  often  so 
seedlike  in  ap- 
pearance that  it  is 
popularly  taken 

for  a  naked  seed.     The  fruit  of  the  Buttercup 

is  a  good  example  (Fig.  260).     Its  nature,  as 

a  ripened  pistil  (in  this  case  a  simple  carpel), 

is  apparent  by  its  bearing  the  remains  of  a 

style  or  stigma,  or  a  scar  from  which  this  has 

fallen.     It  may  retain  the  style  and  use  it  in 

various  ways  for  dissemination  (Fig.  261). 
321.   The  fruit  of  Compositse  (though  not 

of  a  single  carpel)  is  also  an  achene.     In  this 

case  the  pericarp  is  invested  by  an  adherent 

calyx  tube,  the  limb   of  which,  when  it  has   261    Acnei,e  of  Clematis, 

any,  is  called  the  PAPPUS.      This  name  was 

first  given  to  the  down  like  that  of  the  Thistle, 

but  is  applied  to  the  limb  of   the   calyx,  in 

whatever  form  it  appears,  of  the  "compound 

flower."     In  Lettuce,  Dandelion  (Fig.  263),  and  the  like,  the  achene 


260.  Achene  of  Buttercup 
the  right,  opened 
show  the  seed. 


the  style  retained 
as  a  plume  for 
purposes  of  dis- 
persal by  winds. 


150 


THE  FRUIT 


262  263 

262,  263.  Achenes  :  262, 
of  a  Thistle,  pro- 
vided with  a  pap- 
pus for  wind-dis- 
semination; 263, 
of  a  Dandelion, 
the  pappus  borne 
on  a  long  beak. 


264.         265.    Samara 
An  Acorn,    of  the  Elm. 


as  it  matures  tapers  upwards  into  a  slender  beak,  like  a  stalk  to  the 
m       Pappus. 

f-  ;^  *&%•   ^  carv°Psis>  or  Srain>  is  like  an  achene 

with  the  seed  adhering  to  the  thin  pericarp 
throughout,  so  that  both  are  incorporated  into 
one  body ;  as  in  Wheat,  Indian  Corn. 
I  323.    A  nut  is  a  dry  and  indehiscent  fruit, 

I  commonly  one-celled  and  one-seeded,  with  a 
\ \  hard,  crustaceous,  or  bony  wall,  such  as  the 
™  Cocoanut,  Hazelnut,  Chestnut,  and  the  Acorn 
(Fig.  264).  Here  the  involucre,  in  the  form  of 
a  cup  at  the  bas6j  is  called  the  CUPULE.  In 

tlie  Chestnut>  near   relative  of   the   Oak,  the 

cupule  forms  the  bur ;   in  the  Hazel,  another 

relative,  a  leafy  husk. 
324.   A    samara,    or 

key    fruit,    is   either    a 

nut  or  an  achene,  or  any 

other  indehiscent  fruit,  furnished  with  a  wing, 
like  that  of  Ash,  and  Elm  (Fig.  265).  The 
Maple  fruit  is  a  pair  of  keys  (Fig.  266). 

325.  Dehiscent  fruits, -or  pods,  are  of  two 
classes,  viz.,  those  of  a  simple  pistil  or  carpel, 

and  those  of  a  compound  pistil.     Two  common  sorts  of  the  first  are 
named  as  follows :  — 

326.  The  follicle,  a  fruit  of  a  simple  carpel, 
which    dehisces    down    one    side    only,    i.e.   by 
the    inner   or   ventral    suture.      The    fruits    of 

Marsh  Marigold  (Fig.  267) 
are  of  this  kind. 

327.   The     leg- 
ume  or  true  pod, 

such    as    the    Pea 

pod     (Fig.     268), 

and    the    fruit    of 

the      Leguminous 

or     Pulse    family 

generally,     which 

opens     along    the 

dorsal  as  well  as 

the  ventral  suture. 

The  two  pieces  into  which  it  splits  are  called 
VALVES.  A  LOMENT  is  a  legume  which  is  con- 
stricted between  tho  seeds,  and  at  length  breaks 
up  crosswise  into  distinct  joints,  as  in  Fig.  269. 


266  267 

266.  Fruit  of  the  Maple. 

267.  Follicle  of  the  Marsh  Mari- 

gold. 


268 

268.  A  Legume. 

269.  ALoment. 


THE  FEU  IT 


151 


271. 


328.  The  pods  or  dehiscent  fruits  belonging  to  a  compound  ovary 
have   several  technical  names  :    but   they  all  may  be  regarded   as 
kinds  of 

329.  The  capsule,  the  dry  and  dehiscent  fruit  of  any 
compound  pistil.     The  capsule  may  discharge  its  seeds 
through  chinks  or  pores,  as  in  the  Poppy,  or  burst  irregu- 
larly in  some  part,  as  in  Lobelia  and  the  Snapdragon; 
but  commonly  it  splits  open  (or  is  dehiscent)  lengthwise 
into  regular  pieces,  called  VALVES. 

330.  Regular  dehiscence  in  a  capsule  takes  place  in 

two  ways,  which  are  best  illustrated 
in  pods  of  two  or  three  cells.  It  is 
either 

Loculicidal,  or,   splitting   directly 
into  the  loculi  or  cells,  that  is,  down  the  back  (or 
the  dorsal  suture)  of  each  cell  or  carpel,  as  in 
Iris  (Fig.  270)  ;  or 

Septicidal,  that  is,  splitting  through  the  parti- 
tiong  or  septat  ag  in  gt>  JohnVwort  (Figt  271), 

Rhododendron,    etc.      This    divides    the   capsule 
into    its    component    carpels,    which   then    open 
by  their  ventral  suture. 

331.  In  loculicidal  dehiscence  the  valves  naturally  bear  the  parti- 
tions on  their  middle  ;  in  the  septicidal,  half  the  partition  is  borne  on 
the  margin  of  each  valve.     See  the  annexed  diagrams,  Fig.  272.     A 


270.  Capsule 
of  Iris. 


John's-wort! 


272.  Diagrams  of  the  various  modes 
of  dehiscence :  a,  loculicidal ; 
6, septicidal ;  c,  d,  septifragal. 


274 


273,  274.  Fruit  of  the  Fig :  273,  fruit 
laid  open  ;  274,  a  part  magnified 
to  show  the  minute,  interior 
flowers. 


variation  of  either  mode  occurs  when  the  valves  break  away  from  the 
partitions,  these  remaining  attached  in  the  axis  of  the  fruit.  This  is 
called  septifragal  dehiscence. 

332.  The  syconium,  or  fig  fruit  (Fig.  273),  is  a  fleshy  axis  or 
summit  of  stem,  hollowed  out,  and  lined  within  by  a  multitude  of 
minute  flowers,  the  whole  becoming  pulpy,  and,  in  the  common  fig? 
luscious. 


152  THE  FEUIT 


THE   SEED 

333.    Seeds  are  the  final  product  of  the  flower,  to  which  all  its  parts 
and  offices  are  subservient.     Like  the  ovule  from  which  it  originates, 
a  seed  consists  of  coats  and  kernel. 

334.   The   seed   coats    are    commonly  two, 
the  outer  aud  the  inner.     Fig.  275  shows  the 
two,  in  a  seed  cut  through  lengthwise.     The 
outer  coat  is  often  hard  or  crustaceous,  whence 
275.  a,  hilum;  6,  testa;    ^  ig  called  the  testa,  or  shell  of  the  seed;  the 
c,  inner  coat;  d,    inner  is  almost  always  thin  and  delicate, 
albumen;  e,  em-         335.    The  shape  and  the  markillgs,  so  vari- 
ous in  different  seeds,  depend  mostly  on  the 

outer  coat.  Sometimes  this  fits  the  kernel  closely;  sometimes  it  is 
expanded  into  a  wing,  as  in  the  Trumpet  Creeper  (Fig.  276,  a),  and 
occasionally  this  wing  is  cut  up  into  shreds  or  tufts,  as  in  the  .Catalpa 
(Fig.  276,  ft)  ;  or  instead  of  a  wing  the  seed  may  bear  a  coma,  or  tuft 
of  long  and  soft  hairs,  as  in  the  Milkweed  or  Silk  weed 
(Fig.  276,  c).  The  use  of  wings  or  downy  tufts  is  to  render 
the  seeds  buoyant  for  dispersion  by  the  winds.  This  is 
clear,  not  only  from  their  evident  adaptation  to  this  pur- 


276.  Seeds  fitted  by  outgrowths  of  the  testa  for  dispersion  by  the  winds : 
a,  Trumpet  Creeper;  6,  Catalpa;  c,  Milkweed. 

pose,  but  also  from  the  fact  that  winged  and  tufted  seeds  are  found 
only  in  fruits  that  split  open  at  maturity,  never  in  those  that  remain 
closed.  The  coat  of  some  seeds  is  beset  with  long  hairs  or  wool. 
Cotton,  one  of  the  most  important  vegetable  products,  since  it  forms 
the  principal  clothing  of  the  larger  part  of  the  human  race,  consists 
of  the  long  and  woolly  hairs  which  thickly  cover  the  whole  surface 
of  the  seed.  There  are  also  crests  or  other  appendages  of  various 
sorts  on  certain  seeds.  A  few  seeds  have  an  additional,  but 
more  or  less  incomplete,  covering  outside  of  the  real  seed 
coats,  called  an 

336.  Aril,  or  arillus.  —  The  loose  and  transparent  bag 
which  incloses  the  seed  of  the  White  Water  Lily  (Fig.  277) 
is  of  this  kind.  So  is  the  mace  of  the  Nutmeg.  The  aril  is 
a  growth  from  the  extremity  of  the  seed  stalk,  or  from  the 
placenta  when  there  is  no  seed  stalk. 

A  short  and  thickish  appendage  or  outgrowth  around  the  micropyle 
in  certain  seeds  is  called  a  CARUNCLE  (Fig.  278). 


THE  FRUIT  153 

The  various  terms  which  define  the  position  or  direction  of  the 
ovule  (erect,  ascending,  etc.)  apply  equally  to  the  seed :  so  also  the 
terms  anatropous,  orthotropous,  campy lotropo us,1  etc.,  as 
already  denned,  and  such  terms  as 

HILUM,  or  scar  left  where  the  seed  stalk  or  funiculus 
has  fallen  away,  or  where  the  seed  was  attached  directly 
to  the  placenta  if  there  was  no  seed  stalk. 

RAPHE,  the  line  or  ridge  which  runs  from  the  hilum 
to  the  chalaza  in  anatropous  and  amphitropous  seeds. 

CHALAZA,  the  place  where  the  seed  coats  and  the  kernel 
or  nucellus  are  organically  connected,  —  at  the  hilum  in  orthotropous 
and  campylotropous  seeds,  at  the  extremity  of  the  raphe  or  tip  of 
the  seed  in  other  kinds. 

MICROPYLE,  answering  to  the  foramen  or  orifice  of  the  ovule. 


ECOLOGY  OF   THE   FRUIT   AND   SEED   AS   REGARDS   DIS- 
SEMINATION 

337.  The  word  dissemination  here  signifies  the  scatter- 
ing of  the  seeds.     In  a  vast  number  of  cases  not  only  the 
seeds,  but  the  entire  fruits,  are  dispersed,  the  pericarp  fur- 
nishing the  same  protection  to  the  seed  that  it  provided 
during  the  period  of   ripening,  and   furthermore  aiding 
directly  by  its  construction  in  the  transportation  or  even 
in  the  planting  of  the  seed. 

338.  The  need  of  seed  dispersal  is  plain,  both  for  the 
parent  plant  —  which  should  not  be  crowded  by  its  own 
offspring  —  and  for  the  interests  of  the  seedlings  them- 
selves.    That  an  advantage  is  to  be  won  through  wide  dis- 
tribution of  seed  is  shown  by  the  fact  that  the  seed  or 
the  fruit  is,  in  most  species,  adapted  to  the  special  work 
of  dissemination. 

339.  The  agents  of  dissemination  are  wind,  water,  and 
animals.     But  a  considerable  number  of  plants  are  quite 
independent  of  external  aid,  being  provided  with  special 
mechanisms  for  throwing  their  seeds  to  a  distance. 

340.  Structures  to  accomplish  dissemination  through  the 
agency  of  the  winds  are  exemplified  by  the  wings  of  the 
Elm   and   Maple  fruits    (Figs.   265,  266),  the   plume  of 

1  For  these  terms  see  the  section  on  the  ovule,  §  280. 


154 


THE  FRUIT 


the  Clematis  achene  (Fig.  261),  and  the  tufted  pappus 
in  the  case  of  the  Dandelion  (Fig.  263).  The  wing  of 
the  Maple  key  does  not  avail  to  carry  the  seed  very  far 
from  the  source,  on  the  average,  as  may  be  seen  if  we 
examine  the  neighborhood  of  a  Maple  tree  when  the  seed- 
lings are  coming  up  in  the  spring.  The  seedlings  are 
very  numerous  near  the  paront,  very  few  at  a  distance  of 
two  or  three  times  the  height  of  the  tree.  But  one  can- 
not fail  to  be  struck  with  the  successful  planting  of  the 
seeds.  Although  not  originally  covered  by  the  soil,  they 
stand  in  multitudes,  rooted  and  growing,  in  spots  where 
the  grass  was  beaten  down  and  matted  before  the  fruits 
fell.  Though  bulky,  the  keys  find  their  way  into  the 
grass  through  the  action  of  the  winds  in  driving  the 
wings  this  way  and  that,  until  the  seed  ends  have  been 

worked  Avell  toward  the  moist  sur- 
face of  the  soil.  This  example 
illustrates  the  fact,  of  common 
occurrence,  that  appendages  of 
the  fruit  may  serve  both  in  dis- 
semination and  in  placing  the  seed 
in  the  position  most  likely  to 
secure  germination. 

341.  In  connection  with  this 
subject,  the  mechanism  of  Ero- 
dium  (Fig.  279)  for  burying  the 
fruit  may  be  mentioned.  The 
elongated  extremity  of  the  fruit 
279.  Fruit  of  Erodium.  On  is  hygroscopic  ;  that  is,  it  absorbs 

the  left  a  single  carpel  J  & 

vapor  of  water  rapidly  in  damp 
weather,  and  exhales  it  in  dry. 
the  changes  being  accompanied 
by  twistings  and  untwistings. 

As  the  fruit  naturally  falls  with  its  weightier  or  seed 
end  toward  the  earth,  these  hygroscopic  movements,  aided 
by  backward-pointing  hairs,  enable  it  to  work  its  waj 
through  grass  or  other  impediments  toward  the  soil,  ant 
finally  even  partially  to  bury  itself. 


in  damp  weather;  at 
the  right,  several  car- 
pels in  the  calyx,  in  dry 
weather. 


THE  FRUIT  155 

342.  The  appendages  of  seeds  securing  dissemination  by 
wind  are  very  similar  to  those  of  fruits  in  many  cases. 
Compare,  for  instance,  the  seed  of  the  Trumpet  Creeper 
(Fig.  276,  a)  with  the  fruit  of  the  Elm  (Fig.  265)  ;  and 
the  seed  of  the  Milkweed  (Fig.  276,  c),  possessing  a  coma, 
or  tuft  of  hairs,  with  the  pappus-bearing  achene  of  the 
Thistle  (Fig.  262). 

343.  Water.  —  The  fruits  of  the   Cocoanut  Palm  are 
originally  covered  with  husks  impermeable  to  sea  water. 
They  sometimes  fall  into  the  ocean,  and  being   carried 
to   distant   strands  are  cast   up  by  the  waves  and  there 
germinate.     In  a  like  manner  the  achenes  of  the  Arrow- 
head (Sagittaria)  —  a  plant  which  is  common  along  the 
margins  of  ponds  —  buoyed  up  by  the  air-filled  cells  of 
the  pericarp,  are  floated  to  a  distance.     In  a  number  of 
species   they  float  for  a  definite  length  of  time  ;    then, 
when   germination  is  about  to  begin,  they  sink   to   the 
bottom. 

344.  Animals. — The  fruits  of  many  plants  are  thickly 
set    with   hooks   suited   to   catch   in   the  fur  of   animals 
(Fig.    280).       The   fruits   are   thus 

separated  from  the  plant  and  car- 
ried away,  to  be  subsequently  re- 
moved by  the  animals  themselves 
or  brushed  off  accidentally.  Nuts 
hidden  away  in  the  ground  by  squir- 
rels must  occasionally  be  left  to 
grow,  either  through  oversight  or 
on  occasion  of  the  death  of  the  de-  28°-  The  f™!t  of  Asri- 
positor.  Then  again,  edible  fruits 

like  the  Cherry,  the  Apple,  and  the  berries  offer  to 
animals  a  substantial  reward  in  return  for  the  service 
of  dispersal. 

345.  Ejection  of  the  seeds  is  not  uncommon.     The  most 
familiar  example  is  that  of  the  Jewelweed,  or  Touch-me- 
not,  the  ripe  pods  of  which,   when   touched,  burst   and 
throw  the  seed  in  all  directions.      The  bursting  is  due 
to   the   sudden  splitting   asunder  and  coiling  up  of  the 


156 


THE  FRUIT 


several  valves,  already   in   a   high   state  of   tension,  the 

touch      which 
produces     the 
explosion 
merely       in- 
creasing     the 
stress  along   the  lines 
of     dehiscence.       The 
opened  valves  of  the  Vio- 
let     fruit,      constricting, 
cause   the  forcible  expul- 
sion of  the  seeds  one  after 
another.     The  hard,  bony 
capsules    of     the    Witch- 

281.  Fruit  of  Witch-hazel  discharging    hazel  (Fig.  281),  contract- 
ing,  squeeze   the   smooth, 

hard  seeds  with  much  force  ;  and  the  seeds  are  shot  to  a 
distance  of  many  feet.1 


Supplementary  Reading 

1.  Plants  that  bury  their  Seeds.     Lubbock's  "  Flowers,  Fruits,  and 
Leaves,"  pp.  85-88. 

2.  The    Fruits   and   Seeds  of  Plants   Parasitic  on  Trees.     Same 
source,  pp.  83,  84. 

3.  Dispersal  of  various  Fruits  and  Seeds.     Same  source,  Chap.  III. 

4.  Dissemination  of  Plants  by  Ocean  Currents  and  by  Migrating 
Birds.     Darwin's  "  Origin  of  Species,"  Chap.  XI,  Dispersal. 


1  If  a  bough  with  the  ripe  but  unopened  fruits  is  hung  on  the  wall  of 
one's  room,  the  force  with  which  the  seeds  are  ejected  and  the  distance 
to  which  they  fly  are  likely  to  be  observed. 

Distances  to  which  seeds  are  ejected  by  several  plants  are  given  by 
Kerner  and  Oliver  ("Natural  History  of  Plants,"  II,  839)  as  follows:  — 

Cardamine  impatiens 3  ft. 

Viola  canina 3  ft. 

Geranium  palustre 8  ft. 

Lupinus  digitatus ." 23  ft. 

Acanthus  mollis 31  ft. 

Hura  crepitans 48  ft. 

Bauhinia  purpurea 51  ft. 


LABORATORY  STUDIES   OF  CRYPTOGAMS         157 


XV.     LABORATORY   STUDIES    OF  CRYPTOGAMS 

[NOTE  :  —  Many  of  the  following  types  may  be  studied  without 
compound  microscopes,  if  good  hand  lenses  or,  better,  dissecting 
microscopes,  are  provided.  In  the  suggestions  for  study  which  fol- 
low, (simple)  following  the  number  of  a  paragraph  indicates  that  the 
simple  microscope  is  to  be  used;  similarly,  (compound)  indicates  that 
a  compound  microscope  is  to  be  used ;  and  (compound  or  simple) 
indicates  that  the  simple  microscope  may  be  used,  but  the  compound 
is  to  be  used  if  available.  ] 

.  346  (Compound).  Nostoc.  Make  a  note  of  the  general  character 
—  form,  consistency,  color,  etc.  —  of  the  masses  in  which  the  plant 
occurs.  Mount  a  bit  of  the  mass  in  a  drop  of  water  on  a  glass  slide, 
cover  with  a  cover  glass,  pressing  the  latter  down  gently,  and  examine 
first  with  a  low,  then  with  a  higher  power  of  the  compound  micro- 
scope. 

What  constitutes  one  single  individual  plant?  How  are  the  indi- 
viduals grouped?  What  is  the  color?  Are  any  cells  distinguished 
by  size  or  other  character  ?  What  holds  the  cells  and  chains  (colonies) 
together?  Draw  one  chain  by  aid  of  the  highest  power  you  have. 

347  (Compound).    Unicellular  Green  Algae:    Pleurococcus,  or  the 
like.     Upon  what  do  the  plants  provided  grow?    Examine  this  sub- 
stratum with  the  hand  lens,  to  see  if  the  individual  plants  causing  the 
green  tinge  on  the  surface  can  be  distinguished.     Then  scrape  a  bit 
of  the  green  film  into  a  drop  of  water  on  a  glass  slide,  cover,  and 
examine  with  different  powers  of  the  compound  microscope,  the  lowest 
first.     Do  you  find  the  plants  single?    In  groups?    If  in  both  ways, 
draw  both.     Is  there  anything  in  the  number  of  plants  in  a  group,  or 
in  the  position  of  the  members  of  a  group,  or  any  other  circumstance, 
to  suggest  to  you  the  way  in  which  these  plants  multiply? 

348  (Simple).    Spirogyra.     Use  the  simple  lens  to  obtain  an  idea 
of  the  actual  size  of  the  plants.     Do  the  filaments  branch?     Are  there 
cross  partitions?     Do  any  parts  of  the  filaments  differ  markedly  from 
others  ?     How  does  the  color  differ  from  that  of  Nostoc,  if  at  all  ? 
What  portion  of  any  cell  bears  the  color?     What  is  the  arrangement 
of  the  color-bearing  bands  (chromatophores)  f 

349  (Compound).     Is  there  more  than  one  chromatophore  in  each 
cell  ?    Draw  a  short  portion  of  one  filament,  using  a  moderate  power. 
Indicate,  without  drawing  all  of  them,  the  arrangement  of  the  chrc- 
matophores. 

350  (Compound).     Select  a  cell  (for  example  a  terminal  cell)  in 
which  the  spirals  are  rather  loose.     Look  for  the  nucleus,  near  the 
center,  a  colorless  body  from  which  colorless  strings  radiate.     If  this 
is  not  distinguishable,  delay  search  until  after  the  following  treatment. 


158          LABORATORY  STUDIES   OF  CRYPTOGAMS 

Place  a  small  drop  of  dilute  (30  per  cent)  eosin  glycerine  at  the  edge 
of  the  cover  glass  so  that  it  will  run  under.  If  the  glycerine  reaches 
the  Spirogyra,  many  of  the  cells  will  now  be  found  with  their  contents 
much  distorted.  Does  it  appear  that  the  contents  are  separable  from 
the  walls  oil  all  sides?  Select  a  cell  slightly  affected.  Is  there  a 
definite  layer  of  substance  in  which  the  chromatophores  are  imbedded  ? 
The  nucleus,  stained  by  the  eosin,  will  now  be  readily  made  out. 
Draw  a  cell  highly  magnified,  showing  a  part  of  one  chromatophore, 
the  nucleus,  and  the  layer  of  living  substance  (protoplasm)  where 
separated  from  the  wall. 

351  (Compound).    If  material  is  provided,  make  drawings  of  con- 
jugating cells,  showing  stages   in   the  process.     Label  the  rounded 
bodies  found  where  conjugation  has  been  effected  zygospores. 

352  (Compound).   Vaucheria.  —  Use  the  hand  lens  to  gain  an  idea 
of  size  and  general  habit.     If  the  feltlike  mass  is  growing  on  earth, 
pick  off  a  little  with  needles,  using  care  to  get  rid  of  soil  in  the 
preparation.     Mount  in  water  under  the  compound  microscope.     Are 
the  filaments  septate  (partitioned),  or  not?     Focus  on  the  upper  sur- 
face.    What  is  the   shape   and  size  of  the  chromatophores   here? 
Focus  down  until  the  side  walls  stand  out  sharply.     Do  the  chromato- 
phores occur  only  near  the  walls,  or  are  they  scattered  throughout  the 
interior  of  the  tubes  ?    Do  the  filaments  branch  ? 

353  (Compound).   Do  you  find  lateral  club-shaped  (not  globular) 
branches,  or  somewhat  swollen  tips  of  filaments,  of  a  very  dark  green 
color  (sporangia)  ?     Are  they  cut  off  by  partitions  (septa)  ? 

354  (Compound).   Look  for  short,  nearly  globular  branches,   in 
company  with  others  more  slender,  lighter  green,  and  somewhat  coiled. 
If  any  of  these  can  be  made  out  clearly  in  all  parts,   draw   them 
(ob'gonia  and  antheridia).     If  the  form  and  attachment  are  not  clear, 
turn  to  the  figure   given   by  the   teacher,  and  with  its  help  decide 
whether  the  oogonia  and  antheridia  are  found  on  the  material  you 
have.     The  species  studied  and  that  represented  in  the  figure  may 
not  be  the  same,  in  which  case  exact  similarity  of  organs  will  not  be 
expected. 

355  (Compound).  Ectocarpus,  exemplifying  the  Brown  Algae. — 
View  with  the  hand  lens,  then  with  higher  magnifications.     Are  the 
main  trunks  more  than  one  cell  in  thickness?     The  branches?    Draw 
a  small,  branching  portion.     Are  there  any  very  short  branches  dis- 
tinguished by  greater  thickness?    If  so,  are  they  .more  than  one  cell 
in  thickness,  or  does  each  branch  consist  chiefly  of  one  large  terminal 
cell,  or  sac,  with  granular  contents?    Draw  both  sorts  of  branches,  if 
found,  labeling  the  many-celled  ones  gametangia,  and  the  saclike  ones 
sporangia. 

356  (Simple).   Rockweed.  —  Make    a    life-size    drawing    from    a 
branching  portion,  to  show  the  habit  of  the  plant.     With  the  hand 


LABORATORY  STUDIES   OF  CRYPTOGAMS         159 

lens   examine   the   thickened   tips.     Have   the   minute   raised  spots 
openings? 

357  (Compound  or  Simple).   With  a  wet  razor  make  a  good  many 
sections,  as  thin  as  possible,  across  the  tips  where  the  raised  spots  are 
thickest,  and  mount  them  in  water.     Have  the  cavities  seen  in  the 
sections,  and  more  or  less  lined  with  dark  bodies  (oogonia),  any  rela- 
tion to  the  little  prominences  before  seen?     Have  the  cavities  (concep- 
tacles)  openings?    Make  a  diagram  two  or  more  inches  in  diameter, 
showing  the  cavity  of  a  conceptacle  as  seen  in  section,  with  opening 
if  any,  and  adjacent  external  surface  of  the  ihallus  (or  general  body 
of  the  plant).     Show  a  few  oogonia  in  proper  proportion  and  form, 
with  some  of  the  long  filaments  that  spring  from  the  walls  of  the  con- 
ceptacle. 

358  (Compound).   Examine  the  oogonia  with  the  compound  micro- 
scope and  draw  if  additional  details  are  found.     Look  in  the  same 
conceptacles  (or  in  others  from  different  plants,  according  to  the 
teacher's  directions)  for  swollen  cells  borne  on  short  filaments,  much 
smaller  than  the   oogonia,  and  distinguished  by  coarsely  granular 
contents  and  orange  color.     These  are  the  antheridia.     If  necessary 
pick  one  of  the  sections  apart  with   needles  —  or  merely  squeeze  it 
enough  under  the  cover  glass  to  break  it  up  —  in  order  to  see  how 
these  antheridia  are  borne.     Make  a  drawing  to  show  this.     Also 
indicate  on  the  diagram  before  made  the  relative  size  and  the  posi- 
tion of  the  antheridia  in  the  conceptacle,     (But  if  antheridia  and 
oogonia  are  not  found  together,  use  two  diagrams.) 

359  (Simple).   Polysiphonia,1  one   of   the  Red  Alga?.  —  Draw  the 
habit  of  the  plant,  enlarged,  as  seen  with  the  lens.     Look  for  dark 
round  bodies  embedded  in  some  of  the  branches  —  the  tetrasporangia. 
Do  they  seem  to  be  somewhat  eccentrically  placed,  or  are  they  situ- 
ated centrally  so  as  to  occupy  the  whole  diameter  of  the  branch  where 
they  occur?     Draw  a  portion  very  much  enlarged  to  show  the  facts. 

360  (Compound).     Are  the    filaments   of   the   thallus  (or   plant 
body)  composed  of  more  than  single  rows  of  cells?     How  do  the 
branches  end?    Into  how  many  separate  parts  (tetraspores)  is  the 
contents  of  each  tetrasporangium  divided?     (It  should  be  said  that 
the  tetraspores  are  so  arranged  that  one  of  them  is  always  hidden 
from  view.)     Draw  a  tetrasporangium  with  a  short  portion  of  the 
thallus  adjoining. 

361  (Compound).   Nemalion,  a  Red  Alga.  —  Draw  a  short  branch- 
ing portion  to  show  the  filamentous  habit.     If  possible  select  a  piece 
bearing  the  small,  rounded  antheridia  at  the  tips.     If  so  directed  by 
the  teacher,  seek  to  identify  carpogonia  and  cystocarps  by  aid  of  the 
figures  provided. 

1  Material  bearing  tetrasporangia  is  to  he  provided. 


160          LABORATORY  STUDIES  OF  CRYPTOGAMS 

362  (Compound).  Bacteria.  —  With  a  needle  transfer  to  a  slide  a 
bit  of  the  scum,  that  gathers  on  water  in  which  vegetable  matter  is 
decaying.     Cover  with  a  cover  glass  and  examine  with  a  high  power. 
The  Bacteria  are  glistening  white  (i.e.  colorless)  bodies  of  small  size 
often  occurring  in  broad  patches  of  gelatinous  matter  (the  matter 
which  holds  the  "  scum  "  together)  in  which  they  are  more  or  less 
evenly  spaced ;  or  occurring  in  chains  or  threads.     Some  may  be  spiral 
in  form  and  exhibit  very  active  motion.     Having  found  the  Bacteria, 
remove  the  cover  glass,  spread  the  scum  out  thin  on  the  slide,  and 
dry  this  preparation  by  holding  it  at  some  distance  above  a  flame. 
When  the  last  bits  of   the  spread  scum  are   about  to  become   dry, 
remove  from  the  heat  and  add  drops  of  gentian  violet  stain.1    After 
a  moment  wash  this  off  with  a  little  water,  cover,  and  reexamine. 
The  various  forms,  now  more  plainly  seen,  are  to  be  drawn. 

For  suggestions  as  to  the  biological  study  of  Bacteria  see  Appendix. 

363  (Compound).  Yeast.  —  Mount  in  water  a  small  bit  of  yeast 
cake,  spreading  the  material  out  thin,  and  examine  with  a  high  power. 
Are  the  yeast  plants  of  uniform  size?     Have  they  any  peculiarity  of 
form,  common  to  all,  or  nearly  all  (i.e.  are  they  uniformly  spherical, 
or  elliptical,  or  ovate,  etc.)?     Have  they  any  common  features  of 
internal  structure?     Having  determined  these  points  in  your  own 
mind,  make  a  drawing  of  a  typical  yeast  plant  of  the  species  you  have, 
the  drawing  to  be  large  enough  to  show  easily  any  internal  features.2 

364  (Compound).   From  material  that  has  been  growing  for  a  few 
hours  in  sweetened  water  (a  teaspoonful  of  sugar  to  a  half  glass  of 
water),  study  the  method  of  multiplication.     Do  the  buds  —  the  new 
individuals  growing  out  from  the  bodies  of  the  old  plants  —  spring 
from  any  particular  region,  as  a  rule?    Draw  in  outline  three  stages 
in  the  budding  process. 

365.  Is  any  action  of  the  yeast  upon  or  in  the  sugar  solution 
to  be  seen?  To  test  this,  drop  small  pieces  of  yeast  cake  into  tum- 
blers of  (1)  sugar  solution,  (2)  water  alone.  In  fifteen  minutes  or 
so  the  result  should  be  observable,  and  within  an  hour  very  marked. 
What  bearing  has  the  action  observed  upon  the  utility  of  yeast  plants 
in  bread  making?  Answer  this  question  in  your  notes  on  this 
experiment. 

366  (Simple).  Bread  Mold  (Rhizopus  nigricans).  —  Use  the  hand 
lens  to  examine  the  moldy  bread  without  disturbing  it,  so  as  to  see 

1  Strong  eosin  solution  may  be  used,  and  it  leaves  the  Bacteria  with  a 
more  lifelike  appearance,  though  not  so  sharply  denned.     If  the  prepara- 
tion is  stained  with  gentian  violet,  washed,  and  thoroughly  dried,  Canada 
balsam  may  be  used  upon  it  and  the  preparation  thus  be  made  permanent. 

2  The  teacher  should  draw  upon  the  board  the  characteristic  form  and 
striations  of  starch  grains  to  be  found  in  the  yeast  cafce,  so  mat  they  may 
not  be  mistaken  for  the  yeast  plants. 


LABORATORY  STUDIES  OF  CRYPTOGAMS         161 

how  the  mold  grows.  Especially  notice  the  growth  on  the  bottom  of 
the  dish  where  the  fungus  is  spreading  away  from  the  bread.  Make 
a  much  enlarged  drawing  to  show  the  groups  of  stalked  sporangia  as 
seen  from  the  side.  Are  these  groups  connected  in  any  way  ?  Are 
there  any  special  organs  for  attachment  to  the  substratum  ?  Is  the 
number  of  sporangia  in  a  group  constant?  Estimate  the  height  of 
the  sporangial  stalks  in  inches.  State  the  magnification  which  your 
drawing  represents. 

367  (Compound).   With  a  needle  carefully  remove  a  bit  of  the 
plant,  selected  from  a  spot  where  both  white  (young)  and  black  (old) 
fruiting  heads  (sporangia')  can  be  seen,  and  mount  in  water,  or  better 
in  alcohol  followed  by  a  drop  of  water.     Use  first  a  low  power,  after- 
wards a  higher  power.     Have  the  threads  partitions  ?    What  is  the 
color  and  appearance  of  the  contents?     Compare  an  unopened  spor- 
angium with   one   where   the   external   membrane   has  given  way. 
What  portion  of  a  whole  head  is  occupied  by  spores?    Answer  by 
drawings;  show  one  of  the  spores  separately,  more  enlarged. 

368  (Compound).    If  material   is  furnished,  draw  two  or  three 
stages  to  illustrate  zygospore  formation. 

369  (Compound).   Water  Molds  :  Saprolegniaceae.  —  Upon  what  is 
the  given  plant  growing  ?     Remove  a  bit  with  forceps  and  needle  to  a 
drop  of  water  on  a  slide.     Examine  with  the  hand  lens,  to  get  an  idea 
of  the  actual  size.     Then  use  low  and  high  powers  of  the  microscope. 
Are  the  hyphse  of  even  diameter  ?    Is  the  protoplasm  dense  or  thin  ? 
What  is  the  shape  of  the  ends  of  the  hyphse?     Answer  these  questions 
in  drawing. 

Do  you  find  certain  branches  filled  with  denser  protoplasm,  and 
somewhat  enlarged  or  club-shaped?  Can  you  find  stages  leading 
to  this  condition?  Are  the  swollen  extremities  (zoosporangid)  sepa- 
rated by  a  partition  from  the  rest  of  the  hyphae?  Find  zoosporangia 
in  which  the  protoplasm  seems  gathered  into  many  definite  masses ; 
others  empty,  with  these  masses  (zoospores)  escaped,  but  still  near 
by.  From  what  point  do  the  zoospores  escape  ?  Draw  an  unopened 
zoosporangium,  and  one  ruptured,  together  with  a  mass  of  the  spores. 

370  (Compound).     Short-stalked,   globular    organs    (slightly  re- 
sembling the  sporangia  of  Bread  Mold)  will  probably  be  found  in 
abundance  in  both  old  and  young  stages.     Are  the  youngest  ones  cut 
off  by  a  wall?    The  oldest?     What  difference  in  the  contents  at  the 
two  different  stages?     You  may  find  gradations  from  one  condition  to 
the  other.     The  organs  are  the  ob'gonia,  and  when  mature  contain  a 
number  of  oospores.     How  many?     Have  the  oospores  walls?    If  so, 
are  they  thicker  or  thinner  than  walls  (if  any)   of  the  zoospores 
before  noted? 

371  (Compound).     Look  for  slender  branches  with  ends  applied 
to  the  oogonia,  and  somewhat  swollen  at  the  point  of  contact.     In 

OUT.   OF  EOT. 11 


162          LABORATORY  STUDIES   OF  CRYPTOGAMS 

some  cases  these  branches  (antheridia)  may  send  tubes  into  the 
oogonia.  The  antheridia  may  grow  from  the  stalks  of  the  oogonia 
themselves,  or  from  the  main  hyphae  close  by. 

Draw  old  and  young  oogonia,  with  contents,  and  antheridia  (if 
found).1 

372  (Simple).    Peziza.     Upon  what  as  a  substratum  does  the  spe- 
cies of  Peziza  furnished  grow  ?     If  the  Peziza  is  small,  use  the  hand 
lens  in  examination.     What  is  the  general  shape?     Is  the  external 
surface  entirely  smooth  ?     Is  the  color  the  same  on  inner  and  outer 
surfaces?     Represent  all  features  of  form  in  a  drawing  considerably 
larger  than  nature,  if  necessary. 

373  (Compound).     Cut  sections  perpendicular  to  the  inner  sur- 
face.    Mount  in  water.     Do  you  find,  with  a  high  power,  elongated 
sacs  containing  a  definite  number  of  rounded  bodies  (spores)  ?    Do 
you  find  many  or  few  such  sacs?     (If  the  sections  are  not  very  thin, 
press  the  cover  glass  down  cautiously  with  a  needle  to  spread  them  out 
thinner.)     How  are  they  situated  relatively  to  one  another  and  to  the 
surface  of  the  plant  ?     They  are  near  which  surface,  inner  or  outer  ? 
How  many  spores  in  each  sac,  or  ascus?   Draw  a  diagram  of  the  Peziza 
in  section,  showing  the  region  of  the  sacs,  and  indicate  some  of  the 
sacs  in  position.     Draw  a  sac  (ascus)  highly  magnified,  with  spores, 
and  the  threads  that  grow  up  between  the  sacs. 

374  (Compound).    Pulling  off  with  forceps  bits  of  the  substratum 
at  the  point  where  the  cup  of  the  Peziza  was  attached,  and  spreading 
these  bits  out  with  needles  in  water  on  a  slide,  you  may  find  the 
threads  of  the  fungus,  which  gather  nourishment  from  decayed  vege- 
table matter.     These  threads  together  form  the  mycelium ;  the  sau- 
cer-shaped  or   cup-shaped    sac-bearing   body  first  examined   is  the 
apotheciunr.     That  layer   of  the  apothecium  in  which  the   sacs  are 
found  is  the  hymemum.    Label  drawings  according  to  the  terms  given. 

375  (Simple).   Microsphsera.2     With  the  lens  examine  the  whit- 
ened patches  of  the  fungus-infested  leaf.     Is  the  whitening  external 
or  internal?     To  decide  this,  wet  the  leaf  with  a  drop  of  alcohol,  and 
scrape  gently  with  a  knife  point.     The   black,  rounded  bodies  are 
perithecia.     Indicate  by  drawing  the  size  of  the  leaf  and  of  the  peri- 
thecia.     Wet  a  bit  of  the  fungus  with  alcohol,  and  remove  with  a 
knife  to  water  on  a  slide.     If  the  material  has  been  dried,  add  strong 
potash  solution  to  the  preparation.     Is  the  white  film  composed  of 
granules  or  of   threads  ?      Examine  the  perithecia  by  transmitted 
light.     Have  they  appendages  ?     Draw  a  perithecium  much  magni- 

1  In   the  same  mount  more  than  one  kind  of  Water  Mold  may  be 
found,  the  species  differing  in  position  and  character  of  oogonia,  and  in 
antheridia  and  sporangia. 

2  Or  any  genus  of  the  group  Erysiphece  ;  perhaps  the  commonest  form 
being  Microsphcera  alni,  the  cause  of  mildew  on  Lilac  leaves. 


LABORATORY  STUDIES   OF  CRYPTOGAMS          163 

fied.  (But  if  the  compound  microscope  is  to  be  used,  delay  drawing 
until  further  examination  has  been  made.) 

376  (Compound).  With  a  moderate  power  reexamine  the  ma- 
terial noting  the  composition  of  the  white  coating  and  the  details 
of  the  perithecia.  Draw  a  perithecium,  showing  one  or  two  appen- 
dages with  care,  and  indicating  the  rest.  Press  down  the  cover  glass 
so  as  to  rupture  some  of  the  perithecia.  Draw  one  of  the  spore-con- 
taining organs.  In  what  essential  respect,  if  any,  does  it  differ  from 
the  ascus  of  Peziza? 

377.  Toadstool,  illustrative  of  Basidiomycetes.  —  Draw  the  habit. 
Cut  smoothly  down  through  the  middle  of  the  umbrella,  so  as  to  split 
the  stem  at  the  junction  with  the  umbrella.  Draw  the  section  of  the 
umbrella  and  summit  of  stem  as  now  seen.  Label  the  radial  folds 
gills  (lamellae) ;  the  part  from  which  they  are  suspended,  the  pileus. 
Do  all  the  gills  extend  from  the  margin  of  the  pileus  to  the  stem  or 
stipe  t  Are  the  inner  ends  of  the  gills  attached  to  the  stipe?  Draw 
a  diagram  of  a  sector  of  the  umbrella  as  seen  from  below,  to  show 
arrangement  of  gills. 

378  (Compound).    With   a  wet  razor   section   a  portion   of   the 
umbrella  so  as  to  get  cross  sections  of  the  gills.     Carefully  wash  the 
sections  from  the  razor  to  a  slide,  cover,  and  examine  with  low  and 
high  powers.     If  small  and  thin-gilled  species  are  used,  sections  need 
not  be  made;   simply  mount  a  piece  of  the  gill  flatwise,  when  the 
spores  will  be  seen,  grouped  in  a  particular  way,  and  at  the  edge  of 
the  piece  the  manner  in  which  the  spores  are  borne  will  probably  be 
seen.     How  many  spores  are  borne  upon  the  same  swollen  hypha  tip 
(basidium)!     How  are  they  attached  to  the  basidium?    Draw  a  basid- 
ium    with    spores.     Make  a  diagram  of  the  cross  section  of   a  gill, 
showing  where  the  spores  are  borne.     Label  the  layer  in  which  the 
basidia  are  founi  hymenium. 

With  needles  dissect  small  pieces  of  the  stipe  and  pileus,  and 
examine  with  the  high  power.  Of  what  microscopic  elements  is  the 
toadstool  made  up? 

379  (Simple).   Lichen.  —  Examine  the  lichen  with  the  hand  lens. 
Is  there  stem  or  leaf,  or  an  appearance  of  a  main  axis  of  growth  ?     Is 
there  indication  of  green   (chlorophyllous)  color?     Are  there  struc- 
tures resembling  the  spore-bearing  portion  of  any  fungus  heretofore 
studied?     Draw  one  of  the  "fruit"  bodies  (apothecia)  as  seen  from 
above,  much  magnified.     The  deeper-colored  layer  nearly  filling  the 
saucer  is  the  hymenium.     Draw  the  apothecium   in  outline  as  seen 
from  the  side. 

380  (Compound  or  Simple).    Detach  an  apothecium,  place  it  in  a 
piece  of  pith  split  to  hold  it,  and  section  it  as  thin  as  possible  with  a 
wet  razor.     Mount  the  sections  in  water,  and  examine  with  the  lens 
or  a  low  power  of  the  microscope.     Draw  the  section  of  the  apothe- 


164  LABORATORY  STUDIES   OF  CRYPTOGAMS 

cium,  with  the  attached  portion  of  the  thallus.  Where  is  the  green 
color  distributed?  (Show  in  drawing.)  Distinguish  small  brown 
bodies  (spore  sacs)  standing  in  large  numbers  perpendicularly  to  the 
inner  surface  of  the  apothecium,  and  indicate  these  in  the  drawing. 
The  layer  in  which  they  occur  is  the  hymenium.  If  possible,  examine 
this  with  a  higher  power,  and  draw  an  ascus  (spore  sac)  with  the  (how 
many?)  spores.  Also  determine  further  the  exact  location  of  the 
green  color,  and  draw  the  green  bodies. 

381  (Simple).    Marchantia:  a  Liverwort.  —  Draw  the  outline  of  a 
single  plant,  as  seen  from  above,  about  twice  the  natural  diameter. 
Distinguish  the  growing  tip  and  the  base  of  the  plant.     Represent 
the  position  and  outline  of  any  structures  produced  from  the  upper 
surface.     Is  there  a  midrib?     Examine  the  upper  surface  with  the 
hand  lens.     What  do  the   cup-shaped  structures  contain?     Draw, 
much  magnified,  labeling  the  receptacle  cupule,  and  the  small  bodies 
within  gemmce.    Are  the  gemmae  easily  detached?    Put  a  drop  of  water 
into  one  of  the  cupules  and  note  the  behavior  of  the  gemmae?     (The 
gemmae  are  best  seen  on  living  plants ;  in  other  material  they  may  be 
absent.)    What  are  the  purpose  and  nature  of  the  gemmae  ?    By  what 
means  are  they  likely  to  be  disseminated? 

382  (Simple).    Examine  the  upper  surface  of  the  thallus  (plant 
body)  with  the  lens.     Have  the  minute  prominences  pores  at  their 
summits?    It  will  be  well  to  use  also  a  low  power  of  the  compound 
microscope  to  settle  this  question  definitely.     Do  the  same  promi- 
nences occur  on  the  under  side  of  the  thallus?     By  what  means  is  the 
plant  attached  to  the  ground?     Draw  a  little  portion  of  the  upper 
surface  as  seen  by  the  hand  lens,  making  the  drawing  large  enough  to 
show  all  discernible  details  clearly. 

383  (Simple) .   Turn  your  attention  now  to  certain  slender  branches 
of  the  thallus,  ending  in  umbrellalike  portions.     Do  you  find  more 
than  one  kind,  as  regards  the  shape  of  the  "  umbrella"  ?     If  so,  repre- 
sent one  sort  in  side  view,  "  stalk  "  and  all.     Draw  both  of  the  "  um- 
brellas" as  seen  from  above.     The  branch  ending  in  free  rays  is  to 
be  labelled  archegonial  branch,  that  ending  in  a  lobed  disk,  antheridial 
branch. 

384  (Simple).   Select  a  branch  bearing  well-matured  sporogonia. 
Remove  the  stalk.     Lay  the  head,  under  side  upward,  on  the  dissect- 
ing stage,  and  study  the  position  of  the  sporangia.     How  are  they 
arranged,  and  to  what  are  they  attached?    Note  the  fringed  sheaths 
that  partly  inclose  them.     Detach  a  sporogonium.     Draw  it  to  show 
the  form,  the  method  of  dehiscence  (press  the  sporogonium  slightly), 
the  relative  length  of  the  stalk,  etc.     What  does  the  sporogonium 
contain  besides  spores  (use  a  high  power)? 

385  (Compound).   The  antheridial  heads  may  be  sectioned  with 
comparative  ease,  and  the  antheridia  studied  under  the  teacher's  direc- 


LABORATORY  STUDIES  OF  CRYPTOGAMS         165 

tion.  Good  preparations  of  the  archegonia,  from  which  the  sporogonia 
originate,  are  more  difficult  to  make.  If  time  allows,  vertical  sections 
of  the  young  archegonial  heads  may-be  made  by  the  pupils;  or  better, 
the-  archegonia  may  be  drawn  from  preparations  provided  by  the 
teacher.  Distinguish  the  central  egg  cell,  the  neck  and  canal. 

386  (Simple).   Moss.  —  Select  a  single  plant,  in  fruit.     Draw  the 
habit  as  seen  with  the  hand  lens.     Examine  with  the  highest  power 
of  the  dissecting  microscope.     Is  there  distinction  of  leaf  and  stem  ? 
Are  the  leaves  petioled?     Have  they  midribs?     With  needles  clear 
away  the  leaves  at  the  point  where  the  stalk  of  the  spore  capsule 
(sporogonium)  originates.     Does  this  stalk  spring  from  the  end  of  a 
shoot  of  the  moss,  or  is  it  a  branch  springing  directly  from  the  side  of 
a  shoot?     Is  there  any  appearance  of  a  joint  or  any  mark  around  the 
base  of  the  stalk?     Are  the  shoot  and  stalk  separable? 

387  (Simple).    Look  for  a  capsule  which  still  bears  on  its  summit 
a  loose  cap,  the  calyptra.    Draw  the  capsule,  much  enlarged.     Remove 
the  calyptra.     Examine  the  now  exposed  end  of  the  capsule  with  a 
strong  lens.     Do  you  find  any  appearance  of  a  lid,  or  cover,  by  the 
removal  of  which  the  capsule  may  be  opened  ?     Draw  the  outlines  of 
this  part  of  the  capsule,  labeling  the  lid  operculum.     Slight  pressure 
may  force  the  latter  off.     Teeth  standing  within  the  edge  of  the  open- 
ing may  be  seen.     Note  the  quantity  and  appearance  of  the  spores. 

388  (Compound).    With  the  compound  microscope  examine  the 
protonerna  of  the  moss,  if  this  is  provided,  and  draw  a  portion.     Look 
for  buds,  or  beginnings  of  new  leafy  shoots. 

389  (Simple  or  Compound).    If  ready  mounted  sections  of   the 
flower,  so  called,  are  provided,  the  archegonia  and  anlheridia  may  be 
studied  under  the  teacher's  direction.    At  least,  the  shoot  tips  bearing 
these  organs  should  be  examined  with  a  lens,  and  then  dissected  care- 
fully with  needles  in  a  little  water  under  the  dissecting  lens.     By 
skillfully  removing  the  leaves  that  form  more  or  less  of  a  rosette 
around  the  desired  parts,  and   by  further  separation  if  necessary, 
archegonia  and  antheridia  may  be  distinctly  seen,  together  with  the 
sterile  filaments,  or  paraphyses,  that  grow  up  with  them  on  the  end  of 
the  stem. 

390  (Simple).   Fern.  —  1.    The  prothallium.     Place  a  young  prothal- 
liutn  on  the  stage  of  the  dissecting  microscope,  without  water.     Ex- 
amine rapidly  with  the  lens.    Are  the  upper  and  under  surfaces  alike? 
Is  the  protliallium  of  equal  thickness  throughout?     By  what  means  is 
the  plant  attached  to  the  soil  ?     Add  water.     If  soil  particles  still  ad- 
here, remove  carefully  with  a  small  wet  brush  or  with  needles.     The 
general  form  reminds  you  of  what  cryptogamous  plant  before  studied? 
In  what  respects  (refer  to  former  drawings)  ?     Which  is  the  younger 
extremity  of  the  prothallium? 

Turn  it  under  side  upwards  and  view  by  transmitted  light.     Draw 


166          LABORATORY  STUDIES   OF  CRYPTOGAMS 

the  outline  (  x  3-5)  ;  mark  the  margin  at  the  bottom  of  the  chief  notch 
as  the  growing  point.  Indicate  by  shading  in  the  proper  place  any 
thickened  portion,  and  mark  this  cushion.  Show  the  root  hairs,  or 
rhizoida. 

391  (Compound  or  Simple).    Antheridia.     Small  prothallia  should 
show  the  antheridia  plainly  under  the  simple  lens,  especially  if  the 
(living)  material  is  first  treated  with  aqueous  iodine  for  two  or  three 
minutes  and  then  washed.     The  antheridia  are  seen  as  small  round, 
brown  bodies.     Indicate  their  position  and  relative  size  on  the  draw- 
ing already  made.      With  the   compound    microscope   the   general 
structure  of  these  organs  can  be  made  out  probably  without  section- 
ing, and  a  drawing  may  be  made. 

392  (Compound  or  Simple).    Archegonia.     Older  prothallia  may  be 
required.     Treat  with  iodine,  as  before.     With  a  low  power  the  pres- 
ence and  distribution  of  the  archegonia  (appearing  as  numerous  short 
columns  of  cells  projecting  from  the  cushion)  may  be  made  out.     In 
many  of  the  older  and  over-ripe  archegonia  a  central  cell,  embedded 
in  the  prothallium  at  the  base  of  the  projecting  neck,  is  seen  as  an 
opaque,  brownish  sphere.     Indicate  the  position  and  number  of  the 
archegonia  on  the  diagram  before  drawn. 

The  details  of  structure  will  require  higher  powers  and  sections  of 
the  prothallium,  either  provided  already  mounted,  or  made  under  the 
teacher's  directions. 

393  (Simple).     2.    Origin  of  the  spore-bearing  plant.     From  the  ma- 
terial provided  find  out  from  what  part  of  the  prothallium  the  leafy 
shoot  springs.     Is  there  a  root?  and  if  so,  does  it  originate  from  the 
tissue  of  the  prothallium  or  from  the  new  shoot?     Answer  these  ques- 
tions in  a  drawing  (  x  2-4). 

394  (Simple).     3.    The  spores.     Examine  a  "fruiting"  leaf  of  the 
mature  plant.     Are  the  "  fruit  spots  "  (sori,  sing,  sorus)  on  the  upper 
or  under  side  ?     Have  they  a  definite  location  upon  the  divisions  of 
the  leaf?    Indicate  the  facts  in  an  outline  sketch.     Pick  oft*  a  leaf 
segment  and  placing  it  on  the  dissecting  stage  under  the  lens,  with 
needles  carefully  raise  the  covering  (indusium)  of  a  sorus.     Estimate 
the  number  of  spore  cases  (sporangia)  found  beneath.     Have  they 
stalks?     If  you  have  no  high-power  instrument,  draw,  highly  magni- 
fied, all  the  details  you  can  discern  with   the  simple  microscope. 
Much  can  be  made  out  in  this  way.     Draw  (1)  the  sorus  covered  by 
the  indusium  (if  present),  (2)  the  group  of  sporangia  uncovered. 

395  (Compound).    If  high  powers  are  at  hand,  further  examine 
sporangia  and  spores,  after  removing  from  the  leaf  with  a  knife  point 
and  mounting  in  water  in  the  usual  way. 

396  (Simple).  Selaginella.  —  With  hand  lens  examine  the  arrange- 
ment and  shapes  of  the  leaves,  and  draw  a  short  section  of  the  shoot 
( x   3-4)  to  show  these  points.     Do  the  shoots  of  Selaginella  grow 


LABORATORY  STUDIES   OF  CRYPTOGAMS         167 

upright  or  more  or  less  prostrate?  Has  the  leaf  arrangement  any 
relation  to  the  habit  of  growth  ?  Look  for  special  leafless,  root-bearing 
branches. 

397  (Simple).     Do  you  find  the  tips  of  some  of  the  shoots  modi- 
fied (fruiting  spikes)  ?     The  leaves  of  these  spikes  differ  in  what  ways 
from  those  of  the  rest  of  the  plant?     In  their  axils  are  the  rounded 
sporangia.     On  the  stage  of  the  dissecting  microscope,  in  a  few  drops 
of  water,  dissect  a  fruiting  spike  with  needles.     Pull  off  some  of  the 
leaves.     Do  the  sporangia  come  away  with  them  ?    Make  a  drawing 
to  show  the  facts.     Let  the  drawing  be  large  enough  to  show  the  form 
of  the  sporangium  clearly. 

398  (Simple  or  Compound).     Crush  some  of  the  sporangia;  what 
do  they  contain  ?     If  possible,  see  these  very  numerous  bodies  (spores) 
with  a  good  power  of  the  compound  microscope.     Do  they  resemble 
anything  you  have  seen  in  flowering  plants  ? 

399  (Simple).  Look  over  the  fruiting  spikes  for  sporangia  con- 
siderably larger  than  those  already  seen.  Determine  from  a  number 
of  cases  whether  they  occur  with  the  lower  or  the  upper  leaves  of  the 
spike ;  on  one  side  of  the  spike  only,  or  on  all  sides.  Draw  one  of 
these  sporangia  (how  many  protuberances)  ?  Open  it ;  how  many 
bodies  (spores)  contained? 

Having  now  seen  the  two  sorts  of  sporangia,  label  the  one  produc- 
ing small  spores,  microsporangium ;  the  other,  macrosporangium. 
Indicate  roughly  the  relative  size  of  small  spores  (microspores)  and 
large  spores  (macrospores)  in  drawing. 

400  (Simple).  Club  Moss,  Lycopodium.  —  Sketch  the  general  habit, 
to  show  the  attitude  of  the  main  and  branch  stems.     Are  there  dis- 
tinct fruiting  spikes  in  the  species  studied?    If  so,  are  they  raised  on 
stalks,  or  not?     Show  these  points  in  the  habit  drawing.     Compare 
herbarium  specimens  of  a  few  different  species  with  regard  to  the 
same  features.     Does  the  material  furnished  show  any  roots?     If  so, 
show  them  in  the  habit  drawing.     Are  the  leaves  petioled  ?    Are  they 
evenly  distributed  around  the  stem? 

401  (Simple).     Dissect  under  the  lens  a  fruiting  spike.     Do  you 
find  sporangia?    How  many  to  each  leaf  ?     Draw  one  of  the  leaves  to 
show  the  facts.     On  which  surface  of  the  leaves  are  the  sporangia 
borne,  upper  or  under?     Press  one  of  the  sporangia;   what  does  it 
contain?    Look  at  the  bodies  emitted  with  the  compound  instrument. 
Have  they  any  resemblance  to  any  bodies  produced  by  Phanerogams  ? 
Do  you  find  more  than  one  size  of  sporangium  and  of  the  spores? 
Would  the  number  of  spores  in  any  sporangium  be  represented  in 
10's,  in  100's,  or  in  1000's? 

402  (Simple).  Horsetail,  Equisetum.  —  Find  the  leaves.   If  the  main 
axis  bears  offshoots  of  any  sort,  determine  whether  these  are  leaves,  or 
stems,  or  both.     Make  a  drawing  to  show  the  facts,  and  another  of 


168  CRYPTOGAMS 

the  cone  terminating  the  fertile  shoot.  Dissect  the  cone  under  the 
lens.  Note  the  peculiarly  modified  leaves :  how  many  saclike  folds 
has  each?  Is  the  number  constant?  What  is  the  nature  of  these 
"folds  "  as  determined  by  the  contents  ?  Draw  a  diagrammatic  longi- 
tudinal section  of  one  of  the  cone  leaves,  much  enlarged. 

403  (Compound).  With  the  compound  microscope  examine  the 
contents  of  the  sacs.  Draw.  Allow  some  of  the  spores  to  dry  on  a  slide, 
and  then,  while  viewing  them  through  the  microscope  with  a  low 
power,  breathe  out  gently  so  that  the  moisture  from  the  breath  will 
strike  the  spores.  Describe  the  action  seen,  illustrating  by  diagrams. 

XVI.    CRYPTOGAMS 

404.  The  plants  to  be  described  in  the  present  chapter 
are  a  few  chosen  from  a  very  great  number  of  forms, 
making  up  a  series  which  differs  in  many  important  re- 
spects from  the  group  of  Phanerogams.     Cryptogams  on 
the  whole  are  smaller  than  Phanerogams.     It  is  true  that 
the  Ferns  (cryptogamous  plants)  are  a  conspicuous  element 
of  land  vegetation  almost  everywhere,  and  in  the  warmer 
regions  attain  to  the  stature  of  trees ;  and  that  Seaweeds, 
some  of  them  of  great  size,  hold  exclusive  possession  of 
the  littoral  rocks  and  the  borders  of  the  ocean  bed.     But 
the  great  majority  of  cryptogamic  forms  are  too  small  to 
attract  attention,  and  many  are  even  too  minute  to  be  seen 
by  the  naked  eye.     Although  many  of  the  Cryptogams, 
both  great  and  small,  have  a  very  varied  life  history  and  a 
structure  that  is  by  no  means  very  easy  to  understand,  yet 
as  a  group  the  Cryptogams  are  structurally  simpler  than 
the  Phanerogams. 

405.  Viewing  all  cryptogamic  plants  together,  we  find 
that  they  fall  into  a  kind  of  series,  which,  if  followed  in 
one  direction,  leads  toward  the  general  type  of  organization 
found  in  Flowering  Plants ;  or,  in  the  other  direction,  leads 
toward   the    simplest  microscopic   forms.     The   series  is, 
however,  a  very  imperfect  one,  broken  by  many  gaps. 
Next  to  the  Phanerogams  stand  Selaginella  (Fig.  353), 
Lycopodium  (Fig.   357),  and  similar  plants,  with  stem, 
leaf,  root,  and  even  structures  answering  to  rudimentary 
flowers.     A  little  further  removed  come  the  true  Ferns 


CRYPTOGAMS  169 

(Fig.  345).  Still  less  like  Flowering  Plants,  but  closely 
allied  to  the  Ferns,  stand  the  Mosses  and  Liverworts 
(Figs.  340,  334).  In  the  groups  named  —  found  at  what 
we  speak  of  as  the  upper  end  of  the  cryptogamic  series  — 
the  stem-and-leaf  type  of  structure  prevails.  In  the  lower 
groups  a  contrast  in  this  respect  will  be  noted. 

406.  Going  below  the  Liverworts  —  i.e.  away  from  the 
Phanerogams  —  we  come  to  the  Algae  (Seaweeds  and  the 
like,  Figs.  291,  298),  between  which  and  the  Liverworts 
the  similarity  is  not  marked.     The  Algse  include  all  green 
(chlorophyllous)  plants  below  the  Liverworts,  down  to  the 
smallest  and  simplest  (Fig.  282).     Along  with  them,  and 
often  resembling  them  in  many  respects,  are  the  Fungi,  of 
which  ordinary  molds  and  toadstools  are  examples.    Fungi 
lack  chlorophyll. 

407.  In  the  Algse  and   Fungi  the  plant  body  is  not 
distinguished  as  in  Flowering  Plants  and  higher  Crypto- 
gams  into   axis   or   stem,   and   leaves.      It  is  a  simpler 
structure,    and    is    termed    a    thallus.      In    the    simplest 
Cryptogams   the   thallus  is  the  single   cell    constituting 
the  individual  ;    in  higher  forms  it  becomes  a  filament, 
membrane,  or  solid  mass.     Algse  and  Fungi  together  are 
termed  Thallophytes. 

408.  The  Algse  fall  into  four  grand  divisions,  conven- 
iently distinguished  in  most  cases  by  the  color.     In  the 
lowest  group  the  green  due  to  chlorophyll  is  more  or  less 
modified  by  the  presence  of  a  blue  pigment ;  in  the  second 
group  the  chlorophyll  gives  its  true  hue;    in  the  third, 
green  is  masked  by  brown ;  and  in  the  fourth,  a  red  pig- 
ment is  usually  present  to  obscure  the  green  more  or  less 
effectually.     The  description  of  typical  Cryptogams  will 
begin  with  the  simplest  Algae. 

Throughout  the  present  chapter  merely  the  structures 
and  processes  most  commonly  found  in  the  groups  selected 
will  be  described.  Let  it  be  understood  that  a  full 
account  of  even  the  few  forms  brought  forward  would 
involve  many  qualifying  additions  to  the  general  state- 
ments now  made. 


170  CRYPTOGAMS 

BLUE-GREEN   ALGJE 

409.  On  wet  walls  of  stone  and  on  undisturbed  moist 
earth  may  often  be  found  small,  rounded,  jellylike  masses 
of  a  greenish  or  bluish  color.     A  bit  placed  under  the 
microscope  shows  a  great  number  of  chains  of  rounded 

cells  (Fig.  282),  embedded  in  the 
gelatinous  matter.  Certain  cells 
of  each  chain  are  somewhat 
larger  and  lighter  colored  than 
the  rest.  When  a  chain  breaks 
282.  A  chain  of  Nostoc  cells:  in  pieces,  as  occasionally  happens, 

h,  heterocyst;  d,  recent  , .  ,,         .    ,  , 

divisions.  separation    usually    takes    place 

next  to   one   of   these   enlarged 

cells,  or  heterocysts.  The  fragments  finally  develop  into 
chains  of  the  original  character.  The  cells  increase  in 
number  by  transverse  division  (Fig.  282,  d).  Cell  divi- 
sion is,  in  fact,  the  ordinary  process  by  which  the  plants 
of  this  group  multiply. 

410.  If  the  substratum  on  which  the  plants  are  grow- 
ing dries  up,  the  investing  mass  of  gelatinous  substance 
hardens  in  proportion  as  it  parts  with  water,  and  so  be- 
comes a  protective  coating  which  enables  the  plant  to 
withstand  extreme  drought. 

411.  The  plant  here  described  and  figured  (Nostoc)  is 
representative  of  the  Blue-green  Algae   in  color,  in  the 
filamentous  arrangement  of  the  cells,  in  the  method  of 
multiplication  by  transverse  fission,  and  in  throwing  off 
mucilaginous  matter  from  the  Avails  to  form  sheaths  and 
embedding  masses.     In  some  species,  however,  the  cells 
are  found  in  small  groups,  not  filamentous  ;  and  in  others 
the   gelatinous   coating   is   either  very  thin   or   entirely 
wanting. 

412.  Oscillatoria  (Fig.  283)  is,  like   many  of  the   group,  often 
aquatic,  either  floating  freely  or  gathered  in  small  tufts.     The  filaments 
have  a  characteristic  motion  of  bending  slowly  from  side  to  side  — 
whence  the   name  Oscillatoria.     They  also  possess   some  means  of 
locomotion,  by  which  they  slip  along  over  the  substratum,  while  at  the 
same  time  slowly  revolving  upon  the  longer  axes  of  the  filaments. 


CRYPTOGAMS 


171 


New  filaments  arise  from  short  portions  (hormogonia}  with  rounded 
ends  (Fig.  283,  h),  when  these  portions  have  been  set  free  from  the  old 
filaments. 


283.   Oscillatoria :  a,  part  of  a  filament  showing  hormogonia  (A,  A)  ;  c, 
filaments,  less  magnified. 

413.  The  Blue-green  Algse  comprise  a  large  number  of  species, 
many  of  which  differ  considerably  in  general  habit  from  the  forms 
just  described. 

GREEN  ALGJE 

414.  The    Green   Algse    (so    called    from   their   pure 
chlorophyll  green  color)  are  mainly  small  aquatic  plants, 
and  chiefly  inhabit  fresh  waters  ;   though  some  of  them 
are  sub-aerial.     The  smallest  members  are  distinguishable 
only    with    the    microscope  ;     the   largest   form   growths 
several  inches  in  diameter.1     The  exceedingly  numerous 
species  vary  widely  in  structure  and  mode  of  life.     The 
few  here  described  will  give  some  idea  of  the  chief  types. 
It  should  be  understood  at  the  outset  that  only  the  most 
important  facts  of  life  history  are  given  ;    and   that   in 
many  of  the  forms  modes  of  reproduction,  not  here  de- 
scribed, exist. 

415.  Pleurococcus.  —  Almost  all  surfaces  that  are  occa- 
sionally wet  and  are  not  too  much  exposed  to  heat  and 
drying  —  as  shaded  sides  of  tree  trunks,  rough  posts,  and 
rocks  —  after   a   time    become 

green  by  the  growth  of  mi- 
nute unicellular  plants  of  vari- 
ous kinds.  They  thrive  and 
multiply  in  rain,  and  dew,  and 
resist  ordinary  drying.  One 
of  the  commonest  of  these  unicellular  forms  is  Pleuro- 
coccus (Fig.  284).  The  plant  is  simply  a  microscopic 


284.   Pleurococcus. 


1  For  example,  the  familiar  Sea  Lettuce  of  the  seashore. 


17! 


-Jtx 

Or    THE 

UNIVERSITY 


OF 


CRYPTOGAMS 


sphere.  Its only  known  mode  of  reproduction  is  by 
division.  That  is,  each  individual  divides  by  a  cross 
wall,  and  the  two  new  individuals  so  produced  increase  in 
size.  Before  they  separate  they  may  each  again  divide  ; 
and  in  fact  the  plants  are  commonly  found  cohering  in 
small  colonies  (Fig.  284,  B). 

416.  Ulothrix.  —  The  fine  unbranched  filaments  of  Ulo- 
thrix  are  abundant  in  fresh  water,  where  they  grow 
attached  to  stones,  sticks,  etc.  (Fig.  285,  a).  The  fila- 
ments increase  in  length  by  the  division  and  elongation  of 
any  or  all  of  the  cells.  When  Ulothrix  is  about  to  repro- 
duce, its  cells  divide  internally,  so  that  within 
each  one  are  produced  several  cells  ;  but  the 
latter  have  no  cell  wall  formed  about  them. 
When  these  naked  cells  escape,  by  the  rupture 
of  the  mother  cell  wall,  it  is  seen  that  they  are 


285.   Ulothrix:  a,  a  young  filament;   b,  larger  zoospore;   c,  escape  of  these 
spores ;  d,  e,  escape  and  conjugation  of  smaller  zoospores.  —  DODEL-POBT. 

provided  with  hairlike  organs  called  cilia,  by  means  of 
which  they  swim  energetically  about  (Fig.  285,  6,  d). 
The  motile  cells  (called,  from  their  animal-like  power 
of  locomotion,  zoospores)  are  of  two  kinds,  large  and 
small.  The  larger  have  four  cilia  (Fig.  285,  6).  After 
a  short  active  period  they  settle  down,  lose  their  cilia, 
invest  themselves  with  cell  walls,  and  germinate  by 
growing  out  into  new  filaments.  The  smaller  zoospores 
are  provided  with  but  two  cilia.  After  swarming  they 
fuse  (Fig.  285,  e),  generally  in  pairs.  This  process, 
wherein  two  cells  unite  to  form  the  germ  of  a  new  plant, 
is  called  conjugation.  The  body  formed  by  the  conjuga- 
tion of  two  similar  cells  is  a  zygospore.  In  the  case  of 


CRYPTOGAMS  173 

Ulothrix  the  zygospore  forms  a  wall  about  itself,  rests  for 
a  time,  then  makes  some  growth  by  elongating  and 
enlarging,  and  finally  its  contents  break  up  into  several 
zoospores  which  are  like  the  larger  ones  described  above 
and  develop  in  a  similar  fashion. 

417.  Spirogyra. —  Spirogyra  may  be  found  floating  in 
unattached  masses  at  the  surface  of  almost  any  sunny 
pool  or  spring  in  warm  weather.  It  is  often  known  as 
Frog  slime  or  Frog  spittle.  Under  the  microscope  a  bit 
of  the  mass  becomes  a  tangle  of  beautiful  green  filaments, 


286.   Spirogyra:  n,  nucleus;  s,  chromatophores. 

unbranched,  and  consisting  of  elongated  cylindrical  cells 
(Fig.  286)  placed  end  to  end.  In  the  cells  of  Spirogyra 
the  essential  parts  of  the  typical  vegetable  cell  are  well 
seen.1  The  wall  is  lined  with  a  thin,  layer  of  living 
matter  (protoplasm*),  embedded  in  which  are  several 
spiral  bands  of  denser  composition,  the  chromatophores,  or 
color-bearing  organs  (s),  containing  the  chlorophyll. 
Near  the  center  of  the  cell  is  found  the  rounded  nucleus 
(n),  from  which  strands  of  protoplasm  run  to  the  peripheral 
layer.  The  remaining  space  is  filled  with  cell  sap  — 
water  with  dissolved  substances. 

418.  The  cells  of  the  filament  live  in  apparent  inde- 
pendence of  one  another,  each  forming  its  own  food 
supplies,  and  every  one  capable  of  dividing  transversely 
to  form  two  daughter  cells  ;  by  which  process  the  plant 
increases  rapidly  under  favorable  conditions. 

1  Refer  here  to  §§  494-498  ;  a  full  discussion  of  the  cell  should  "be  hail 
at  this  point.  Emphasize  the  relative  unimportance  of  the  wall ;  the 
idea  of  the  living  unit  having  the  nucleus  as  the  center  and  conservator  of 
vital  activity  ;  the  r61e  of  the  nucleus  in  cell  division  (briefly);  arid  the 
occurrence  of  many  cells  (represented  by  nuclei)  in  a  common  wall,  as  in 
Vaucheria  next  to  be  described. 


174 


CRYPTOGAMS 


419.  Growth  and  reproduction  should  now  be  clearly 
distinguished.  Growth  is  the  increase  in  size  of  an 
already  existing  individual ;  reproduction  is  the  forma- 
tion of  a  new  individual,  or  new  individuals.  In  the 
case  of  Pleurococcus  cell  division  results  in  the  produc- 
tion of  two  new  individuals,  which  separate  sooner  or 
later.  In  the  growing  root  tip  of  a  Flowering  Plant, 
on  the  other  hand,  cell  division  is  merely  a  step  in  the 
formation  of  more  root,  and  is  therefore  only  a  growth 
process.  In  the  case  of  Spirogyra,  if  we  consider  the 
whole  filament  to  be  the  individual,  then  division  of  the 
several  cells  is  to  be  regarded  as  growth.  But  if  the  cells 
of  the  filaments  are  considered  to  be  the  individuals,  i.e. 
essentially  independent  organisms,  their  division  must 
then  be  regarded  as  reproduction.  The  two  processes  here 
run  together,  since  it  is  not  easy  to  say  how  much  of  the 
plant  may  be  termed  the  individual. 

420.  Reproduction.  —  Under  certain 
conditions,  however,  the  cells  of  Spi- 
rogyra take  part  in  a  distinctly  repro- 
ductive process.  The  cells  of  a  filament 
send  out  lateral  processes  which  meet 
similar  processes  from  cells  of  another 
filament  (Fig.  287).  Cells  thus  become 
united  in  pairs.  Openings  are  then 
made  in  the  conjoined  outgrowths,  by 
which  the  contents  of  all  the  cells  on 
one  side  pass  over  into  those  on  the 
other.  The  contents  of  each  pair  of 
— =-j  I  cells  unite  to  make  up  a  single  body, 

287.  Conjugation   of    Or  zygospore  (zs),  which  becomes  invested 

Spirogyra :  zs.     -,,-,•   i  ,  • 

zygospore;    f,    uj  a  thick  wall  preparatory  to  a  resting 

fusion  in  pro-    period.     In  this  form  the  plant  endures 

periods    of    drought,    when    the    pools 

where  it  grows  dry  up;  and  thus  it  also  passes  the  winter. 

421.    Here,  as   in   Ulothrix,  two  similar  cells  unite  in 

reproduction.     In  plants  soon  to  be  described  the  fusing 

cells  differ  largely  in  size  and  other  characteristics. 


CRYPTOGAMS 


175 


288.  Desmids. 


422.  Conjugation    of    similar    unciliated    reproductive 
cells  is  characteristic  of  a  considerable  group  of  Green 
Algse.     Fresh  water  preparations  very  often  contain 
unicellular   forms   belonging   to   this   group,  more 

or  less  resembling  the  species  represented  in  Fig. 

288.  Sometimes   they  cohere  in  chains.     Usually 
they  are  capable  of  slow  locomotion.      They  are 
Desmids. 

423.  Vaucheria.  —  The  green  filaments 
of  Vaucheria  are  large  enough  to  be  dis- 
tinguished by  the  naked  eye.    By  repeated 
branching    they    form    upon    moist    soil 
matted    growths  which    may   be    several 
inches  in  diameter.     The  plant  also  grows 

submerged  in  water.  The  filaments  are  continuous  tubes, 
ordinarily  without  cross  partitions  (i.e.  unseptate'),  and 
are, lined  with  a  protoplasmic  layer  in  which  numerous 
nuclei  and  small  rounded  chromatophores  are  held;  the 
main  cavity  of  the  tubes  being  filled  with  cell  sap  as  in 
the  case  of  Spirogyra  cells.  In  fact  the  thallus  of  Vau- 
cheria is  to  a  certain  degree  such  as  would  be  produced 
if  the  cells  of  Spirogyra  were  not  separated  by  end  walls, 
the  chief  differences  in  this  respect  being 
the  greater  number  of  nuclei,  the  shape 
of  the  chlorophyll  bodies,  and  the 
branching  habit  of  Vaucheria. 

424.  Reproduction.  —  Zoo  spores  are 
produced  in  the  ends  of  side  branches 
after  these  portions  have  been  cut  off 
by  septa  and  thus  converted  into  zoospo- 
ranqia.  The  whole  contents  of  each 

289.  Zoospore       and 

zoosporangium    zoosporangium    escapes   by  the   rupture 

of  the  wal1  at  the  aPex  CFig-'  289)>  and 
constitutes  a  single  large  zoospore  pro- 
vided with  numerous  pairs  of  cilia  distributed  over  its 
surface.  The  motile  period  may  last  for  several  hours, 
after  which  time  the  cilia  are  lost,  a  wall  is  formed  around 
the  zoospore,  and  germination  very  soon  takes  place  by 


176 


CRYPTOGAMS 


the  protrusion    of   one  or  two  tubular  filaments,  which 

grow  directly  to  new  plants. 

425.    Zoospores  are  apt  to  be  formed  when  the  plant  is 

growing  in  a  submerged  situation.     In  places  where  it  is 

exposed  to  the  air  and  moistened  only  occasionally,  as  by 
the  dew,  a  second  method  of  repro- 
duction prevails.  Swellings  arise 
on  the  thallus,  which  develop  into 
short,  thick  branches  of  peculiar 
form.  When  cut  off  by  septa 
below  they  become  the  oogonia 
(Fig.  290,  og).  The  contents  of 
the  oogonium  contracts  somewhat 
to  form  the  egg  cell,  and  an  open- 
ing makes  its  appearance  in  the 
oogonium  wall.  Near  by,  short, 
slender,  often  coiled  branches  grow 
up.  Their  extremities  are  cut  off 


Vaucheria :  A,  the  un- 
opened antheridium 
(a)  and  oogonium 
(og) ;  B,  the  same 
after  fertilization 
and  formation  of  to  form  the  anthendia  (rig.  290,  #), 

from    which     antherozoids,    bodies 
small 


the    oospore    (os) .  — 
PBINGSHEIM. 


resembling  small  zoospores,  are 
finally  liberated.  The  latter  make  their  way  through 
water  to  the  opening  of  the  oogonium,  and  one,  enter- 
ing, fuses  with  the  egg  cell.  The  resulting  body,  or 
oospore,  now  surrounds  itself  with  a  cell  wall  and  enters 
a  resting  state.  It  is  ultimately  set  free  by  the  rupture 
of  the  oogonium  wall,  and  germinates. 

426.  In  Vaucheria  we  have  essentially  the  same  reproductive  pro- 
cesses as  in  Ulothrix,  but  now  appearing  in  a  much  modified  form. 
The  single  large  zoospore  of  Vaucheria,  with  its  many  cilia,  performs 
the  same  office  as  the  numerous  small  zoospores  of  Ulothrix.    The  pro- 
duction of  the  oospore  in  Vaucheria  may  be  likened  to  the  union  of 
reproductive  cells  in  Ulothrix,  with  the  important  difference  that  now 
the  fusing  cells  differ  greatly  in  size,  and  only  one  of  them  is  motile. 

427.  Cells   designed  for  reproductive   union   are   called  gametes. 
When  they  are  of  unequal  size,  the  larger  is  termed  egg  cell  or  simply 
egg ;  the  smaller,  if  motile,  is  an  antherozold.     The  egg  is  said  to  be 
fertilized  by  the  antherozoid.     The  body  directly  resulting  from  the 
\mion  of  unequal  gametes  is  an  oospore. 


CRYPTOGAMS 


177 


BROWN  ALGJE 

428.  The  Brown  Algge  (Fig.  291)  are  almost  exclusively- 
salt-water  plants.  They  are  in  most  cases  attached.  In  size 
they  range  from  microscopic,  unicellular  forms,  through 
the  fine  filamentous  species  (Fig.  291,  D),  to  thalloid 
forms  of  immense  length.  "  Of  these,  Macrocystis  pyrifera 


291.  Brown  Algae:  A, the  Sea  Colander  (much  reduced) ;  B,  Larainaria  (much 
reduced) ;  C,  the  Gulf  Weed  with  floats  (a) ;  D,  Ectocarpus  (magni- 
fied), s  being  sporangia. 


is  noted  for  its  gigantic  size  :  rising  obliquely  upward  to 
the  surface  of  the  water  from  the  sloping  sides  of  eleva- 
tions in  the  ocean  bed,  its  floating  thallus  has  a  length  of 
600  to  900  feet.  The  stalk  below  is  naked,  but  at  the 
surface,  where  it  streams  out  horizontally,  it  bears  many 
long  pendent  segments,  each  provided  at  the  base  with  a 

OUT.   OF  EOT. 12 


178  CRYPTOGAMS 

large  bladderlike  float  filled  with  air." 1  The  Gulf  Weed 
(Fig.  291,  C),  which  collects  in  such  quantities  in  the  so- 
called  Sargasso  seas,  belongs  to  this  group.  On  certain 
coasts  it  grows  as  an  attached  plant.  Portions  which  have 
been  detached  and  carried  off  by  currents  continue  to  grow 
and  multiply  vegetatively  as  they  float  in  the  quieter  areas 
of  the  ocean. 

429.  The  brownish  color  of  the  Brown  Algse  is  due  to 
a  pigment  in  the  cells,  which  probably  aids  the  chlorophyll 
present  in  the  work  of  assimilation. 

430.  Reproduction.  —  Reproductive  cells  are  of  several 
sorts  in  this  group.     First  and  simplest  are  the  zoospores 
borne   in    Zoosporangia    (Fig.    292,   A),    found   in   most 

members  of  this 
g^P-  Their  Ms- 
tory  is  like  that 
of  the  larger  zoo- 
spores  of  Ulo- 
thrix ;  that  is, 
they  germinate 

292.  A,    zodsporangium,    and    B,  gametangium,  of   directly  after 

Ectocarpacese ;  C,  gametes  (g)  and  their  con-   swarming1,     witll- 
iugation  (s) .  —  PRINGSHEIM. 

out  fusion. 

431.  Secondly.     We  find  processes  of  cell  fusion,  not 
unlike   those   already   seen   in    the    reproductive   bodies 
of    Green   Algae.     We   may   select   three    representative 
cases.     (1)   In   Ectocarpus   and  allied   plants,  zoospores 
(gametes)  are  produced,  which  are  indistinguishable  from 
the  zoospores  intended  for  direct  germination,  except  that 
the  bodies  now  in  mind  arise  in  sporangia  of  a  different 
character  (Fig.  292,  B).    They  may  conjugate  in  pairs  (C), 
like  the  small  zoospores  of  Ulothrix.      (2)  In  some  forms 
(Cutleria),  the  fusing  zoospores  (gametes)  differ  in  size. 
The  larger  come  to  rest  before  fusion.     This  is  a  step 
intermediate  between  the  condition  in  Ectocarpus  and  that 
next  to  be  described.     (3)  In  the  common  Rock  weed  of 
the   shores,   the   gametes   are   egg   cells  and  antherozoids 

1  Strasburger,  "Text  Book  of  Botany,"  p.  330. 


CRYPTOGAMS 


179 


(Fig.  297).  The  egg  cells  are  produced  in  od'gonia 
(Fig.  295),  found  in  cavities  or  conceptacles  (Fig.  294), 
which  make  their  appearance  at  cer- 
tain seasons  in  special  portions  of  the 
branching  thallus  (Fig.  293).  The 
antherozoids  originate  in  antheridia 


293.  A  Branch  of  Rock- 
weed  :  /,  a  fertile 
portion. 

—  THURET. 


294.  Section  of  a  conceptacle.  —  THURET. 


(Fig.  296),  enlarged  cells  produced 
on  branching  filaments.     The  anther- 

idial  filaments  grow  from  the  walls  of  conceptacles,  either 
with  the  oogonia,  or  in  other  conceptacles  upon  separate 
plants,  according  to  the  species  of 
Rockweed  considered.  At  maturity 
both  egg  cells  and  antherozoids  escape 
from  the  concepta- 
cles and  float  about. 
The  antherozoids 
swarm  about  the 
naked  egg  cell  ener- 
getically (Fig.  297), 
and  one  of  them 

^fi^W^lliFN     ^na^y  penetrates  and 
fuses    with    it.      At 
An  oogouium.  —  once    a   wall    begins 

THURET.  tQ    form    about    t]ie    fertilized    egg,     or 

oospore,  which  now  settles  to  the  bottom,  and  upon  ger- 
mination gives  rise  to  a  new  plant. 


296. 


295. 


An  autheridial 
branch ;  a,  au- 
theridia. 

—  THURET. 


180 


CRYPTOGAMS 


432.  From  the  series  given 
above  (Ectocarpus,  Cutleria, 
Rockweed)  it  is  apparent 
that  the  antherozoids  in 
Rockweed  are  in  the  nature 
of  reduced  zoospores  ;  while, 
the  egg  cell  also  answers  to 
a  zoospore,  only  in  this  case 
the  cell  is  of  increased  size, 
and  being  from  the  first; 

297.  Antherozoids  swarming    about    deV°id    °f     cilia>    is     entirely 
the  egg  cell.  —  THUBBT.  passive. 


RED  ALGJE 

433.  The  Red  Algse  (Fig.  298)  are,  with  few  excep- 
tions, marine. 1  While  many  forms  may  be  found  in  very 
shallow  water,  many  are  found  in  deep  water  where, 
owing  to  the  feeble  light,  no  other  algse  can  exist.  In 


298.  Red  Algae:  A,  Delesseria  sinuosa; 
B,  the  so-called  Irish  Moss ;  C,  2. 
fresh- water  species,  Batrachosper- 
mum  ccsrulescens ;  D,  two  fila- 
ments of  the  last,  showing  the 
cells. 

some  of  the  smallest  and  simplest  species  the  thallus  con- 
sists of  loose  branched  filaments  (Fig.  298,  D);  in  others, 
as  in  the  Irish  Moss  (Fig.  298,  B),  the  flattened  thallus  is 
divided  into  narrow  segments ;  while  in  many  others,  the 

1  Of  fresh-water  species.  Batrachospermum,  Fig.  298,  C,  is  very  common 
on  stones  in  brooks. 


CRYPTOGAMS 


181 


plant  body  is  very  thin  and  much  expanded,  and  reaches  a 
length  of  several  feet.  In  most  cases  the  plants  are 
attached  by  more  or  less  rootlike  holdfasts.  The  often 
beautiful  color  is  due  to  the  presence  of  a  red  pigment, 
which  more  or  less  completely  masks  the  chlorophyll. 

434.  Reproduction.  —  A  characteristic  method  of  bearing 
spores  is  in  groups  of  four  (Fig.  299),  each  group  result- 
ing from  the  division  of  the  contents  of 

an  original  mother  cell.  Such  spores  are 
termed  tetraspores.  They  are  bright  red 
bodies  without  cell  walls,  and  being  un- 
provided with  cilia,  are  dependent  upon 
water  currents  for  dissemination. 

435.  Reproduction,  with  fusion  of  the 
reproductive  cells,  may  be  illustrated  by 
the  case  of  Nemalion ;  this  being  taken 
as  a  simple  instance  of  a  process  which 

e  in   some    members    of 

the     group     becomes 
highly      complicated. 
The  reproductive  cells  of  Nemalion  are 
pollinoids,   naked   spherical  cells    pro- 
duced   singly    in    rounded    antheridia 
(Fig.  300, a),  and 
differing  from  an- 
therozoids  only  in 
being    unciliated ; 
and  egg  cells  formed 
within     elongated 
cells  termed  carpo- 
gonia  (Fig.  300,  <?). 
The  egg  occupies 
the  enlarged  basal 
portion  of  the  car- 
pogonium,  the  hair- 
like    extremity   of 
Several  pollinoids, 


299.  Tetraspores  («) 
in  a  filament 
of  Polysipho- 
nia. 


B  O 

300.  Nemalion:  A,  showing  the  earpogonium  (c), 
trichogyne  (t)  with  pollinoids  near,  and 
antheridia  (a) ;  B,  after  fertilization,  the 
carpogonium  beginning  to  hranch ;  G,  the 
nearly  mature  spore-bearing  body  (cysto- 
carp,  c?/).  —  THUBET. 

which  is  known  as  the  trichogyne  (f). 


brought  by  circulation  of  the  water,  may  adhere  to  the 


182  CRYPTOGAMS 

trichogyne  ;  they  surround  themselves  by  membranes,  and 
the  contents  of  one  of  them  passes  through  the  trichogyne 
wall  and  makes  its  way  to  the  egg  cell.  After  fertilization 
the  fertilized  egg  (oospore),  remaining  in  position,  divides 
and,  on  all  sides,  sends  out  branches  (Fig.  300,  c),  from 
which  separable  cells,  called  carpospores,  are  finally  formed. 
These  spores  serve  the  same  purpose  as  the  tetraspores, 
growing  directly  to  new  plants. 

436.  It  is  to  be  noted  that  while  in  Vaucheria  and  Rockweed  the 
oospore  is  set  free  from  the  parent  plant  before  germination  and 
grows  directly  to  a  new  plant,  in  Nemalion  the  corresponding  body 
(fused  egg  cell  and  pollinoid)  is  not  liberated  from  the  carpogonium, 
but,  as  we  may  say,  germinates  in  position.     The  free  spores  are  pro- 
duced only  after  an  interval  of  growth. 

437.  We  summarize  reproduction  in  the  types  of  Green,  Brown, 
and  Red  Algse  as  they  have  here  been  described,  as  follows  :  — 

(1)  Reproductive  cells  give  rise  to  new  plants  without  conjugating. 
A  single  cell,  set  free  from  the  parent,  germinates  without  having  to 
fuse  with  another  cell.     This  single  cell  is  a  spore :  in  Ulothrix  and 
Brown  Algse,   a  zoospore;    in   Red   Algae,  a  tetraspore  or  a  carpo- 
spore. 

(2)  Reproductive  cells  conjugate  before  giving  rise  to  new  plants. 
Two  cells  unite  to  make  up  a  body  which  is  the  starting  point  of 
a  new  plant.     The   uniting  cells   are  gametes.     Gametes   may  be : 
(a)  zobspores  (zoogametes),  indistinguishable   in  some  cases  from  the 
zoospores  which  germinate  without  conjugating;  (b)  pairs  of  similar 
unciliated  cells  (Spirogyra);   (c)  egg  cells  and  antherozoids  or  polli- 
noids   (Vaucheria,    Rockweed,    Nemalion).     The    egg   cell    may   be 
fertilized  in  position  (Vaucheria,  Nemalion),  or  after  liberation  (Rock- 
weed).     The  immediate  result  of  conjugation  is  a  zygospore  when  the 
uniting  cells  are  alike ;  an  oospore,  when  they  are  unlike.     The  oospore 
may  be  freed  from  the  oogonium  before  it  germinates  (Vaucheria, 
Rockweed),  in  which  case  the  reproduction  is  described  as  oosporic ; 
or  may  develop  in  position  (Nemalion),  carpospores  being  the  indirect 
result,  in  which  case  the  reproduction  is  said  to  be  carposporic.     In 
Vaucheria  and  Rockweed  the  germination  of  the  oospore  gives  a  new 
plant;  we  may  properly,  therefore,  think  of  the  structure  resulting 
from  the  fertilization  of  the  egg  in  Nemalion  (namely,  the  branches 
of  the  carpogonium  and  the  carpospores  while  forming)  as  a  new 
plant  parasitic  upon  the  parent. 

(3)  Reproduction  without  conjugation  serves  for  rapid  propagation ; 
and  at  the  same  time  for  dispersion,  since  the  spores  are  often  motile, 
and  when  unciliated  float  easily  in  the  water. 


CRYPTOGAMS  183 

(4)  Reproduction  with  conjugation,1  in  the  Algae  and  other  low 
plants,  is  often  associated  with  exposure  of  the  plant  to  adverse  con- 
ditions, such  as  the  approach  of  winter  or  drought  or  the  old  age  of 
the  plant.  It  seems  to  be  a  mode  of  reinvigorating  the  species  at  the 
moment  when  the  production  of  a  new  plant  is  to  be  provided  for. 
It  is  clearly  of  the  same  nature  as  the  fertilization  of  the  egg  cell  in 
the  ovule  of  the  Flowering  Plants. 

Reproduction  with  conjugation  (sexual  reproduction)  in  the  Thallo- 
phytes  is  of  three  types,  as  indicated  above;  viz.,  1)  zygosporic, 
2)  oosporic,  3)  carposporic.  An  important  system  of  classification  of 
both  Algae  and  Fungi  (in  which  essentially  the  same  reproductive  pro- 
cesses occur  as  in  Algae)  is  founded  upon  these  types. 


FUNGI 

438.  Fungi  may  conveniently  be   defined   as   Thallo- 
phytes  lacking  chlorophyll.     In  structure  and  life  habit 
many  of  them  closely  resemble  certain  Algae.     In  some 
instances  the  resemblance  is  so  striking  that  we  may  with 
assurance  regard  the  fungal  forms,  in  these  cases,  as  having 
been  derived  from  Algse,   chlorophyll  having  been  lost 
through  the  adoption  of  a  parasitic  or  saprophytic  mode 
of  life.     Parallel  cases  in  Flowering  Plants  are  furnished 
by  the  Dodder  (a  parasite,  Fig.  32)  and  the  Indian  Pipe 
(a  saprophyte,  §  59). 

439.  Many    of    the    species   are   unicellular   and   very 
minute.     When  of  more  than  one  cell,  the  plant  body  is 
generally  filamentous.     Even  in  the  compact,  fleshy  forms, 
like  the  Toadstools,  the  solid  structures  are  built  up  of 
an  immense  number  of  essentially  independent  threads. 
The  vegetative  filaments   of   Fungi   are  termed  hyphce ; 
and  the  plant  body  composed  of  hyphse  (aside  from  special 
spore-bearing  parts)  is  the  mycelium. 

440.  The  number  of  species  of  Fungi   is  very  great, 
and  the  types  are   extremely  various.     A   few  common 
forms  will  be  described  in  order,  thereby,  to  present  sev- 
eral of  the  most  important  groups. 

lrThe  last  two  methods  of  reproduction  are  also  termed  the  asexual 
and  the  sexual  modes,  respectively. 


184 


CRYPTOGAMS 


Bacteria 

441.  The  Bacteria  (Fig.  301)  include  the  smallest  of 
all  living  organisms.     Even  the  highest  powers  of  the 
microscope  fail  to  show  much  of  their  inner  structure  ; 
so  that  at  present  very  little  is  known  of  their  relation- 
ship to  other  groups.     Our  knowledge  is  confined  to  their 
external  forms,  methods  of  multiplication,  and  modes  of 
life,  with  their  effects,  good  and  bad  ;  but  this  knowledge 
is  of  the  highest  practical  importance,  since  the  Bacteria 
affect  the  lives  of  other  living  beings,  including  man,  in 
very  direct  ways. 

442.  Size.     A  common  spherical  form  is  ^oyuoT  ^nc^  ^n 
diameter  ;   the  rod-shaped  germ  of  consumption  is  from 
three  to  nine  times  as  long  as  this  ;  many  species,  however, 

are  considerably  larger.  Form.  The 
principal  forms  are  (1)  spherical, 
(2)  straight  cylindrical,  (3)  spiral. 
Movements.  Many  Bacteria  exhibit 
very  lively  movements.  Locomotion 
is  usually  accomplished  by  means  of 
extremely  fine  cilia  (Fig.  301).  Mul- 
tiplication commonly  takes  place  by 
fission.  Each  individual  divides  into 
two  parts,  by  transverse  division, 
each  part  becoming  a  new  individual. 
Under  favorable  conditions  —  abun- 
dance of  food  and  considerable 


cilia;     b,    a    spiral 
ciliated  form ;   c,  a 


301.  Bacteria,  highly  mag- 
nified :  a,  the  germ 
of  typhoid  fever, 

stained  to  show  the    warmth  —  the    Bacteria  may  double 
in  numbers   about  every  half  hour, 
rod-shaped  form,  in     In  this  way  enormous  multitudes  may 

chains;  d.  a  spheri-  -i,  <•  •    •       i    •     i- 

cai   form. —  a,  &,    result  even  from  one  original  mdi- 

from  ENGLER  and    vidual  in  a  comparatively  short  time. 

Low  temperatures  retard  growth  and 

division  :  hence  the  utility  of  ice  in  preserving  foods  in 
warm  weather.  Under  certain  conditions  Bacteria  pass 
into  a  spore  condition,  in  which  they  become  highly 
resistant  to  destruction  by  heat  or  drying.  In  a  dry 


CRYPTOGAMS  185 

state  the  spores  of  some  species  may  live  for  years.  They 
are  not  necessarily  killed  by  boiling.  Only  repeated  or 
greatly  prolonged  boiling  will  sterilize  liquids,  i.e.  free 
them  from  all  Bacteria  ;  though  a  single  boiling  will  kill 
all  active  Bacteria  present.  Prevalence.  Bacteria  are 
present  in  considerable  numbers  in  ordinary  air  and  in 
most  fresh  waters.  They  are  very  abundant  in  most 
soils.  They  abound  in  many  milk  supplies  and  are  present 
in  butter,  cheese,  and  other  foods.  Subsistence.  Bacteria 
are  (1)  saprophytic  and  (2)  parasitic.  The  parasitic 
species  may  cause  deadly  diseases  in  animals  (including 
man). 

443.  Effects.     Bacteria  bring  about  chemical  changes 
in  the  substances  in  which  they  live.     Such  changes  are : 
the  decay  of  the  dead  bodies  of  animals  and  plants  ;  the 
fermentation  (souring)  of  milk;  the  "ripening"  of  cream 
and  of  cheese  ;  and  the  conversion  of  the  alcohol  in  cider 
into  the  acid  of  vinegar.     In  the  manufacture  of  butter, 
cheese,  and  vinegar,  therefore,  Bacteria  play  an  important 
part.     Other   instances   of   their   usefulness   in   the  arts 
might  be  given. 

Among  diseases  known  to  be  due  to  Bacteria  are  influ- 
enza, erysipelas,  scarlet  fever,  typhoid  fever,  consumption, 
leprosy,  lockjaw,  and  cholera.  The  principal  source  of 
harm  is  the  production  of  virulent  poisons  in  the  blood. 
In  spite,  however,  of  the  dangerous  character  of  the  para- 
sitic species,  the  Bacteria  are  on  the  whole  a  highly  bene- 
ficial group  of  organisms.  The  dissolution  of  dead  organic 
bodies,  and  the  enrichment  and  preparation  of  soils  for 
the  uses  of  higher  plants,  effected  by  Bacteria,  are  very 
important  services. 

Yeasts 

444.  If  one  examines  microscopically  a  small  portion  of 
yeast  cake  sold  for  raising  bread,  he  finds  (along   with 
starch  grains  from  the  potato  used  in  making  the  cake) 
numbers   of   small,   colorless,   unicellular  plants,   broadly 
elliptical  or  somewhat  ovate  in  outline,  and   of   various 


186  CRYPTOGAMS 

sizes  (Fig.  302).  Though  very  small  plants,  the  Yeasts 
are  larger  than  most  Bacteria,  averaging  perhaps  ^lyFo 
inch  in  length.  Each  cell  consists  of 
wall  and  protoplasmic  body,  generally 
including  refractive  granules  and  a 
large  sap  cavity. 

Reproduction. — New  individuals  are 
formed  riot  by  division  into  two  equal 
"Y      parts,  as  in  the  Bacteria,  but  by  a  pro- 
302.  Yeast  plants:  i    cess    of    "budding."     The  cell  wall  is 
and   2   repre-    pushed  out    at    some  point  in  a  small 

sent  successive  -,    j  in.  -,•    -, 

stages  in  the     rounded  swelling,  which    receives  pro- 
process  of  bud-     toplasmic  contents  from  the  parent  cell. 
It  increases  in  size  and  is  finally  cut  oft' 
by  a  new  cell  wall  ;  though  it  may  long  remain  attached 
to  the  parent  cell.     Before  its  separation  it  may  itself  bud 
in  one   or  more  directions,  and   thus   irregular   colonial 
growths  arise.     Yeasts   may   multiply   very  rapidly,  an 
entire  new  generation  appearing  in  a  couple  of  hours. 

There  are  many  different  sorts  of  Yeast.  The  usefulness 
of  all  Yeasts,  however,  depends  upon  their  power  of 
decomposing  certain  sugars,  with  the  resultant  formation 
of  alcohol  and  carbonic  acid  gas  (that  is,  their  power  of 
exciting  alcoholic  fermentation).  In  beer  and  wine 
making,  alcohol  is  the  product  sought ;  in  bread  raising, 
on  the  contrary,  carbonic  acid  gas  is  the  useful  product, 
its  bubbles  giving  the  bread  its  lightness. 


Bread  Mold  (Rhizopus) 

445.  If  fresh  moist  bread  is  placed  in  a  tightly  closed 
dish  in  a  warm  place,  within  a  few  days  a  thick  growth 
of  fine  white  mold  will  probably  make  its  appearance, 
unless  special  precautions  have  been  taken  to  prevent  such 
a  result.  That  the  plant  may  be  secured  without  failure 
by  such  means  of  course  demonstrates  the  prevalence  of 
its  minute  spores  in  the  air,  or  in  the  dust  which  has 
settled  on  the  bread  or  on  the  dishes  used.  If  we  were  to 


CRYPTOGAMS 


187 


follow  a  spore  to  its  destination  and  observe  its  develop- 
ment, we  should  find  that  after  soaking  up  some  of  the 
juices  of  the  bread  it  germinates  by  putting  out  a  trans- 
parent hypha  (Fig.  306).  The  hypha  grows  by  further 
absorption  of  food  matter,  increases  rapidly  in  length, 


303.  Bread  Mold :  S,  a  sporangium ;  r,  rootlike  organs. 

branches  repeatedly,  and  thus  ultimately  develops  into  a 
complex  mycelium  running  over  the  bread  and  sending 
hyphse  into  the  interior.  All  portions  of  this  mycelium 
may  be  in  communication  internally,  for  there  are  no 
cross  walls,  or  septa.  In  this  respect  Rhizopus  is  like 
Vaucheria. 

446.    Reproduction.  —  Special  erect  filaments  are  soon 
sent  up,  at  the  summits  of  which  white  globular  sporangia 


A  B  c 

304.  A,  young  sporangium ;  B,  section  of  a  mature 
sporangium  ;  C,  sporangium  after  rupture  of 
the  exterior  membrane  (w). 


305.  A  spore  of  Bread 
Mold,  more  high- 
ly magnified. 


are  formed  (Figs.  303,  304).  At  maturity  both  turn 
black.  The  numerous  spores  are  ovate  bodies  (Fig. 
305),  covered  with  cell  walls  which  protect  them  from 


188 


CRYPTOGAMS 


the  chief  danger  which  besets  all  very  small  organisms 
exposed  in  the  air,  namely,  drying.  Where  the  Fungus 
spreads  away  from  the  bread  along  the  bottom  of  the 
dish,  it  is  seen  that  the  sporangial  stalks  arise  in  groups 
at  points  where  the  hyphse  touch  the  dish,  at  which 
points  also  rootlike  organs  appear  (whence  the  name 
Rhizopus,  root  footed).  The  whole  has  very  much  the 
habit  of  a  Strawberry  plant  propagating  by  runners 
(Fig.  303). 

A  B 


306.   Germination  of  307.  Conjugation  of  Rhizopus :   A,  B,  C,  D,  suc- 

the  spore.  cessive  stages    in    the    production    of  the 

zygospore. 

447.  Under  certain  conditions   short  lateral  branches 
spring  out  near  one  another  from  neighboring  hyphse  and 
grow  until   their  tips  are  in   contact  (Fig.  307).     The 
end  parts  of  the  branches  become  cut  off  by  septa.     They 
are  the  gametes,  which  fuse  after  the  walls   have   been 
absorbed   at   the   point   of   contact.      The   result   is   the 
formation  of  a  thick-walled  resting  spore,  or  zygospore 
(Fig.  307,  z). 

Water  Molds  (Saprolegniaceae) 

448.  The  best  way  to  secure  material  for  the  study  of 
these  plants  is  to  bring  in  a  large  handful  of  decaying 
leaves  from  some  pond  hole  or  bog  where  water  stands, 
throw  them  into  a  jar  of  water,  and  after  them  throw  in 
either  dead  insects  or  succulent  shoots  of  seedlings  killed 
by  heat.     Upon  these  food  materials  the  spores  of  the 
Water  Molds  from  the  dead  leaves  will  fasten  and  ger- 


CRYPTOGAMS 


189 


minate.  The  short  floating  filaments,  often  much  stouter 
than  those  of  the  Bread  Mold,  may  be  distinguished  by 
the  naked  eye.  Under  the  microscope  they  are  seen  to 
compose  an  unseptate  branching  mycelium,  which  pene- 
trates the  object  upon  which  it  grows. 

449.  Reproduction.  —  The  more  or  less  swollen  ends  of 
some  branches  are  seen  to  be  filled  with  dense  protoplasm 
and  to  be  cut  off  by 

septa  to  form  the 
zoosporangia  (Fig. 
308,  A).  The  con- 
tents finally  breaks 
up  into  numerous 
rounded  bodies  which 
finally  escape  from  a 
terminal  opening  in 
the  zoosporangium. 
These  bodies,  the  zoo- 
spores,  in  some  spe- 
cies are  motile  from 
the  time  they  are  set 
free  ;  in  other  species 
just  after  ejection 
they  surround  them- 
selves by  a  delicate 
cell  wall,  from  which 
they  soon  escape  and 
swim  away,  soon  to 
germinate. 

450.  Resting    oo- 
spores     are      formed 
from    egg    cells,  pro- 
duced    in     spherical 
oogonia     (Fig.     308, 
D),     fertilized     from 

antheridial  tubes  (Fig.  309),  which  penetrate  the  oogonial 
wall  in  order  to  reach  the  egg  cells.  After  fertilization 
the  Qpspore  surrounds  itself  with  a  thick  wall. 


.  Water  Mold:  A,  zoosporangium;  B,  es- 
caped zoospores,  before  becoming  motile ; 
C,  zoospores  in  the  active  stage;  D, 
oogonia  and  antheridia  (a) .  The  lower 
oogonium  contains  an  unfertilized  egg 
cell  (e),  and  two  young  oospores  (o) ;  the 
upper  shows  four  mature  oospores  (sp) . 


190 


CRYPTOGAMS 


310.  Germination  of 
the  oo'spore : 
a,  zoo'sporau- 
gium ;  s,  zoo- 
spores. 
-DE  BARY. 


451.  This  process  differs   from   oospore   formation   in 
Vaucheria  chiefly  in  the  usual  presence  of  several  egg 

cells  in  each  oogonium,  and  in  the  con- 
duction of  the  fertilizing  cells  (or  nuclei) 
to  the  egg  cells  by  means  of  tubes.  In 
Vaucheria,  it  will  be  remembered,  the 
fertilizing  cells  are  an- 
therozoids.  Frequently 

309.   Fertilization  of      .        «,.    ,         ,,   ,-,       ,, 

Water  Mold:     m    Water  Molds   there 

a,  antheridial  is  this  further  peculiar- 
ity, that  without  fertili- 
zation egg  cells  become  oospores  capable 
of  germination. 

452.  It  is  from  resting  oospores  in  the 
dead  leaves  that  the  plant  is   obtained 
for  study,  as  recommended  above.     The 

oospores  on  germinating  shortly  give  rise  to  zoospores 
(Fig.  310),  and  these  infect  the  dead  flies,  etc.,  thrown 
into  the  water. 

Sac  Fungi  (Ascomycetes) 

453.  The  *name    Sac    Fungi    or    Ascomycetes    (ascus, 
sac,   and    mycetes,   fungi)    is    given   from   the    fact    that 
spores  are   borne  in  more  or  less   oval,   club-shaped,   or 
elongated  sacs  at  the  ends  of  hyphse  (Fig.  313).     The 
sacs  may  be  present  in  large  numbers  and  are  generally 
grouped  in  special  structures,  or  "fructifications,"  built 
up  from  the  mycelium   around   the   sac-bearing   hyphae. 
The  following  common  forms  will  serve  to  familiarize  the 
student  with  prevailing  types  of  fructification,  for  it  is 
by  the  forms  of  these  structures  that  the  different  Sac 
Fungi  are  chiefly  distinguished. 

454.  Peziza.  —  Common  species  of  Peziza  are  most  readily 
found  growing  on  rotting  logs  and  sticks,  though  many 
spring  from  the  soil.     Tlie  mycelium  of  septate  threads 
spreads  through  the  substratum  for  absorption  of  decaying 
organic  matter.     The  fructification,  known  as  apothecium, 
is  in  many  species  saucer-shaped  (Fig.  311),  in  others 


CRYPTOGAMS 


191 


bowl-shaped,    or    even    club-shaped.      The   largest   have 
apothecia  several  inches  across,  but  the  commoner  kinds 


311.  Peziza  on  wood. 


312.   Section  of  apothecium; 
h,  hymenium. 


are  a  quarter  inch  or  less  in  diameter.  The  interior  of 
the  saucer  is  lined  by  a  layer  Qiymenium,  Fig.  312)  made 
up  of  spore  sacs  (Fig.  313)  and  sterile  filaments  that 
grow  up  between  them.  When  ripe, 
the  (eight)  spores  escape  by  the  rupture 
of  the  sac  (ascus).  On  germinating,  the 
spores  give  rise  to  mycelia,  the  apothe- 
cia  not  ap- 
pearing for  a 
considerable 
time. 

455.  Micro- 
sphaera  Alni, 
one  of  the 
Powdery  Mil- 
dews, is  par- 
asitic, often 
on  the  leaves 
of  Lilac  (Fig. 
314).  .  The 
my  c  el  i  um 

spreads  over  the  surface  of  the 
leaf  and  sends  haustoria  (suck- 
ing hyphse)  into  the  interior. 
In  the  earlier  part  of  the  season 

Simple   erect   filaments  arise,   at  314.  Lilac  leaf ,  infected  by  Micro- 

tffe  ends   of  which   spores   are 

formed  (somewhat  as  in  Penicillium).     Later,  fructifica- 


313. 


A  part  of  the  hy- 
meniiim,  great- 
ly magnified :  a, 
an  ascus ;  /,  a 
sterile  filament. 


192 


CRYPTOGAMS 


315.  A  perithecium  brok- 
en open  to  show 
the  asci. 


tions  are  produced  on  the  leaf  surface,  appearing  to  the 
naked  eye  as  minute  rounded  black  bodies.  These  are 
the  perithecia  "(Fig-  315)  which  in- 
close the  spore  sacs.  The  perithecia 
bear  radial  appendages. 

456.  Aspergillus,  a  very  common 
fine  mold  on  dry  bread,  cake,  cheese, 
preserved  fruits,  etc.,  should  be  men- 
tioned here,  since,  though  it  is  really 
an  Ascomycete,  it  would  not  be  rec- 
ognized as  such  at  one  stage  of  its 
existence.  On  first  appearing  upon 
the  given  substratum  the  mycelium  sends  up  great  num- 
bers of  erect  branches  ending  in  globular  heads,  from 
which  are  produced  spores  in  chains 
radially  arranged  (Fig. 
316).  At  a  later  stage 
of  its  history  the  myce- 
lium gives  rise  to  small 
rounded  fructifications 
inclosing  the  character- 
istic spore  sacs  of  an 

Ascomycete.      In     like   317-  Fruit  of  AsPer- 

gillus,       with 
manner  other  members  asci  (a). 

of  this  group  are  known  —  KNY. 

to  pass  through  two  stages  of  develop- 

316.  S^tion  of  the  ment  differing  in  the 
method  of  spore  bear- 
ing. Periicillium,  a  very 
common  blue  mold  (Fig. 

318),  is  an  example. 

457.    The    Rusts.  —  Many   Fungi   un- 
dergo remarkable  transformations  in  the 

course  of  their  life  history.     This  is  very 

marked  in  the  case  of  the  Rusts,  of  which 

the   common    Rust    of   Wheat  (Puednia 

r/raminis)  may  be  taken  for  description. 

*'     .     .  .,     J,  .  --t,  318.     Sporophore    of 

It  infests  the  leaves  and  stems  of  Wheat,         peniciiiium. 


sporophore  of 
Aspergillus. — 
KNY. 


CRYPTOGAMS 


193 


Rye,  Oats,  and  various  other  grasses.  The  first  appear- 
ance of  this  Fungus  in  the  spring  that  one  is  at  all  likely 
to  see,  however,  is  not  upon  a  grass, 
but  011  the  leaves  of  the  common 
Barberry,  in  the  form  of  thick- 
ened red  patches.  On  the  under 
side  of  these  areas,  embedded  in 
the  leaf  tissues,  are  then  found  the 
so-called  cluster  cups,  or  fructifica- 
tions (Fig.  319), 

filled  with   chains 

of  rounded  spores. 

New     spores     are 

formed  at  the  base 

of  the  chains  while 

the  terminal  ones 

fall    off    and    are 

carried  by  the  winds  to  the  Wheat  (or 

other  grass).      The  mycelium  produced 

from  these   spores  penetrates   the   body 

of    the   new  host, 

where  it  increases 

largely,      working 

320.  A  stalk  of  grass   damage      to      the 
with  spores  of   Wheat,  and  form- 

Puccinia  break-    .  .-,  f 

ing  through  the  mg  at  tne  surface 
masses  of  spores 
for  the  further 


319.  Section  through  a  clus- 
ter cup  of  Puccinia  in 
the  leaf  of  Barberry. 


epidermis       in 
dark  patches. 


spread  of  the  disease.  The  spores 
produced  on  the  Wheat  are  differ- 
ent both  in  shape  and  in  the  manner 
in  which  they  are  borne  from  the 
spores  of  the  cluster-cup  stage  on 

Barberry.      Moreover,    on    Wheat  32L  Uredospores  and  a  te- 
the  spores  are  of   two   sorts  (Fig. 
321):    (1)  unicellular    uredospores, 
prevailing  until  late  summer  or  fall,  the  office  of  which  is  to 
spread  the  Rust  by  immediate  germination  on  being  blows- 

OUT.  OF  BOT. 13 


leutospore  (£)  of  Puc- 
cinia. —  DE  BARY. 


194 


CRYPTOGAMS 


to  uninfected  plants  ;  (2)  two-celled  teleutospores,  charac- 
teristic of  the  latter  part  of  the  season,  thick-walled,  and 
fitted  to  survive  the  winter.  While  still 
remaining  on  the  dead  stalks  of  the  grain 
in  the  following  spring,  the  teleutospores 
germinate.  Each  cell  puts  out  a  short 
filament  (Fig.  322)  ;  and  on  the  sides  of 
these  filaments  small  spores  called  spo- 
ridia  are  formed.  Finally,  by  these  spo- 
ridia  the  Barberry  leaves  are  infected, 
and  the  life  cycle  is  brought  to  the  point 
at  which  this  description  was  begun. 

458.  Puccinia  graminis  is  one  of  many 
Fungi  adapted  to  different  hosts  at  dif- 
ferent periods  of  their  life  history,  and 
failing  to  develop  if  the  proper  hosts  are 
not  met  with  at  the  particular  stages 
when  they  are  required.  The  sporidia 
of  this  Rust  germinate  only  on  Barberry; 
while  the  cluster-cup  spores  and  uredospores  of  the  same 
Fungus  refuse  to  develop  except  on  certain  grasses 
(Wheat,  Oats,  Rye,  etc.). 


322.  Germination  of 
the  teleuto- 
spore  (t) ;  s, 
s,  the  spo- 
ridia. 
-DE  BARY. 


Basidiomycetes 

459.  The  Basidiomycetes  include  the  Toadstools  and 
Puffballs  and  their  relatives.  The  mycelia  usually  live 
saprophytically  in  soil,  leaf  mold,  decaying  wood,  etc.1 
The  fructifications  which  arise  may  be  simple  layers  of 
tissue,  coating  the  surface  of  the  substratum,  as  in  the 
whitish  or  brownish  incrusting  growths  found  everywhere 
on  the  under  sides  of  rotting  sticks  ;  but  in  the  majority 
of  cases  they  are  stalked  structures. 

In  the  common  Toadstool  (Fig.  323)  the  stalk  (stipes,  s) 
supports  a  cap  (pileus,p)  from  which  depend  radial  gills  (la- 
meUce,  I).  Upon  the  surfaces  of  these  gills  the  sporiferous 


1  Some  Basidiomycetes  are  parasitic ;  for  example,  the  Fungus  which 
causes  on  Azalea  and  allied  plants  the  growths  known  as  "May  Apples." 


CRYPTOGAMS 


195 


layer  Qiymenium)  lies.    Figure  325  shows  part  of  the  cross 
section  of  a  gill.     The  spores  (s)  are  borne,  usually  in  fours, 

on  enlarged  hy- 
pha  tips  called 
b  a  s  i  d  i  a  (B)  . 
This  character 
—  namely,  bear- 
ing spores  on 
basidia  —  has 
given  the  group 
(Basidiomycetes) 
its  name. 

460.  Other  types 
of  fructification.  — 
The  Basidiomyce- 
tes  furnish  the  col-  324- 
lector  a  great  vari- 
ety of  curious  and 
interesting  forms.  A  little  search 
in  almost  any  woods  will  bring 
some  of  them  to  light.  The  hy me- 
nial layer  is  variously  disposed. 
In  some  incrusting  forms  men- 
tioned above  (Corlicium)  it  is  sim- 
ple (not  folded)  ;  in  Clavaria  (Fig. 
326)  it  covers  the  coral-like  branches ;  in  Hydnum  (Fig.  327)  the  hy- 


A  part  of 
the  myce- 
lium. 


323.  Fructification    of   a  toadstool 

(Amanita  phalloides) :  p, 
pileus,  or  cap ;  I,  lamellae,  or 
gills. 


325.  Section  of  a  gill,  highly  magnified :  B,  basidia;  S,  spores. 


196 


CRYPTOGAMS 


menial  surface  is  thrown  into  teeth;  in  the  Pol}- 
porus  sub  group  (Fig.  328)  the  arrangement  is 
exactly  the  reverse,  for  the  hymenium  lines  the 
numerous  pores.  Branches,  teeth,  pores,  and  gills 
are  all  devices  for  increasing  the  extent  of  spo- 
riferous  surface. 


326.   Clavaria. 


327.  Hydnum. 


328.   Polyporus :  p,  pores  of  the 
under  surface. 


LICHENS  (Figs.  329,  330) 

461.  Lichens  form  gray  or  yellowish  patches  on  rocks 
and  trees,  festoons  on  the  branches,  and  incrusting  sheets 
and  spongy  mats  on  barren  soil.  They  are  commonly 

known    as  "  Moss  "  —  a  wholly 
wrong  name,  as  will  be  seen  when 


-a 


329.  A  lichen  (Physcia  stellaris) : 
a,  apothecia. 


330.   Usnea  barbata. 


CRYPTOGAMS 


197 


we  come  to  the  real  Mosses.  A  section  through  a  Lichen 
thallus  (Fig.  381)  shows  large  numbers  of  green  cells 
having  much  the  appearance  of  such  unicellular  Algae  as 
Pleurococcus  and  Nostoc,  held  in  the 
meshes  of  a  tissue  made  up  of  filaments 
resembling  Fungus  hyphse.  These 
appearances  represent  the  truth  of 
the  matter.  Lichens  are  composite 
growths  in  Avhich  certain  unicellular 
Algse  and  certain  Fungi  take  part. 
Figure  332  shows  how  this  union  be- 
gins. The  spore  of  a  Fungus  has 
fallen  near  a  cell  of  Pleurococcus. 
The  young  mycelium  is  already  ap- 
plied to  the  Alga,  which  has  divided. 
Further  development  consists  in.  the 


Section  of  a  lichen 
thallus. 


extension    and    branching    of 
the  mycelium,  and  the  multi- 
plication of  the  algal  cells;  the 
construction,  by  these  means, 
332.  Fh-st  stages  in  the  formation    of    a    thallus    having    certain 
of   the  lichen   thallus.—    distinguishing  peculiarities  of 

BORNET.  ,. 

structure,    according    to    the 

kind  of  Fungus  and  the  kind  of  Alga  concerned ;  and 
finally,  the  production  of  a  spore-bearing  body.  In  many 
Lichens  this  fructification  is  an  apo- 
thecium  (Fig.  329,  a)  very  like  that 
of  Peziza,  with  a  hymenium  con- 
taining spore  sacs  or  asci  (Fig.  333). 
Most  of  the  Lichen  Fungi  are  Sac 
Fungi.  They  are  parasitic  upon 
the  Algse  and  cannot  exist  without  them.  The  Algae, 
however,  are  known  to  be  able  to  exist  perfectly  well 
without  the  Fungi.1 

1  Symbiosis  (as  the  word  is  understood  among  English-speaking 
botanists)  is  the  living  together  of  unlike  organisms  for  mutual  advan- 
tage. Many  botanists  regard  Lichens  as  examples  of  symbiotic  accom- 
modation. 


Section  of  an  apothe- 
cium. 


198  CRYPTOGAMS 


LIVERWORTS  AND  MOSSES    (BRYOPHYTES) 

462.  The  account  of  Chlorophyllous  plants  was  inter- 
rupted at  the  end  of  the  section  on  Red  Seaweeds.    A 
series  of  colorless  forms  (Fungi)  was  then  introduced,  in 
general  structure  and  often  in  detail  closely  resembling 
Algae.    We  return  to  chlorophyll-bearing  plants  at  a  point 
where    the   ascending   line    of   vegetable  life  leaves  the 
waters  to  become  henceforward  very  largely  terrestrial. 

463.  The  words  "  line  "  and  "  series  "  are  not  to  be  understood  in 
too  restricted  a  sense.     For  example,  in  Algae  several  seeming  lines  of 
progressive  development,  running  more  or  less  side  by  side,  are  to  be 
discerned ;  and  the  same  may  be  said  of  any  large  group  of  plants. 
Moreover  the  "  line  "  or  "  series  "  is   never   continuous,  —  is  in   fact 
merely  a  succession  of  considerably  separated  groups,  through  which 
run  certain  general  principles  of  structure.    In  the  grand  series  begin- 
ning with  unicellular  Algae  and  ending  with  Flowering  Plants,  many 
breaks  occur.     That  is,  at  certain  points  new  features  appear  in  the 
plant  body,  not  matched  by  anything  in  any  known  lower  form.    It  is 
not  to  be  imagined  that  the  whole   organization  is  new — that   the 
break  in  the  series  is  absolute.     The  nature  of  the  cells  upon  which 
the  whole  character  of  all  vegetable  life  depends  is  always  the  same, 
and  certain  reproductive  processes  are  always  essentially  the  same. 
By  the  interruption  of  the  series,  we  mean  that  in  considering  the  ori- 
gin of  certain  plants  we  are  unable  to  find  anything  which  we  can 
regard  as  their  near  ancestry  in  the  lower  grades.     This  is  the  con- 
dition in  the  Liverworts.     We  may  suppose  they  sprung  from  an 
algal  stock  ;  for  the  plant  body  is  an  expanded  thallus,  the  habitat  is 
often  damp  earth  or  even  water,  and  reproduction  is  brought  about 
through  fertilization  of  an  egg  cell  by  antherozoids,  as  in  many  Algae. 
But  there  is  nothing  by  which  we  can  fix  the  Liverworts  as  near  rela- 
tives of  any  particular  one  of  the  existing  algal  groups.1 

464.  Marchantia  (Fig.  334),  one  of  the  commonest  of 
the    Liverworts,    is   found   growing    prostrate   upon   the 
ground  in  damp  situations.      The  ordinary  length  is  an 
inch   or   two.      The    thallus   forks   frequently,    and    the 
branches  grow  forward  while  the  oldest  portion  of  the 
thalbis  continually  dies  away  ;  so  that  finally  the  branches 

1  By  some  authorities  the  Liverworts  have  been  regarded  as  related 
to  the  Stoneworts  (  Characece)  or  the  like ;  by  others  to  be  descendants  of 
Algse  resembling  Coleochsete,  the  Water  Shield. 


CRYPTOGAMS 


199 


become  separate  individuals.    The  plant  is  attached  to  the 
ground  by  absorptive  hairs,  or  rhizoids.      Above,  the  sur- 


B 


334.  Marchantia  :  A,  thallus  with  rhizoids  (r),  cupules  (c),  and  archegonial 
branch  (6)  ;  B,  section  of  archegonium,  the  fertilized  egg  (e)  having 
divided  once;  C,  disk  of  fruiting  branch  cut  to  show  sporogonia 
(m,  n,  o)  ;  D,  opened  sporogonium  with  enveloping  sheath  (pe),  and 
remains  of  old  archegonium  (ar). 

face  is  seen  on  close  inspection  to  be  divided  into  small, 

slightly  raised  areas,  each  with  a  pore  at   the   summit. 

The  pore  leads  into  a  chamber  (Fig.  335),  from  the  floor  of 

which   rise   short   fila- 

ments or  rows  of  richly 

chlorophyllous  cells  — 

the    chief  assimilatory 

tissue.      This  arrange- 

ment has  the  same  ef- 

fect as  that  of  the  loose 

tissues    in    the    leaf    of 

Flowering  Plants  (see 

Fig.  382),  where  pores  (stomates)  give  free  passage  to  gases, 

while  the  epidermal  covering  retains  moisture, 


335.   Section  in  upper  part  of    thallus  to 
show  P°re  <P)  and  assimilating  cells 


200 


CRYPTOGAMS 


337' 


465.  Reproduction.  — Upon  the  upper  surface,  over  the 
axes  of  growth,  or  midribs,  small  cup-shaped  structures 
called  cupules  (Fig.  334,  A,  c)  are  found.     From  the  bottom 
of  each,  several  small  lens-shaped  bodies,  composed  of  a  con- 
siderable number  of  cells,  arise  ;  they  are  known  as  gemmce 
(literally  buds).    When  set  free  and  scattered  by  rains  and 
running  water   they   develop   directly   into   new  plants. 
This  is  vegetative  propagation  much  resembling  the  propa- 
gation of  Lilies  by  bulblets  and  various  other  Flowering 
Plants  by  offsets.       Gemmae  serve  the  same  purpose  as 
zoospores  in  the  Algse,  namely,  rapid  multiplication. 

466.  A  second  reproductive  process  is  now  to   be  de- 
scribed, in  which  gametes  much  like  the  equivalent  bod- 
ies in  Algse 

take  part.  In 
late  spring 
and  in  ear- 
ly summer 
erect,  more 

or  less  umbrellalike,  branches  are 
found.  They  are  of  two  kinds.  In 
one  case  (antheridial  branches,  Fig. 
336)  the  termination  is  a  disk  with 
scalloped  margin.  In  the  other  the 
stalks  end  in  a  disk  from  which 
fingerlike  rays 
project  (Fig. 
334) ;  these  are 
the  archegonial 
branches.  In 

depressions  of  the  scalloped  disks 

stand  the  short-stalked  antheridia. 
The  large  cell   of   the    anther- 

idium  (Fig.  338)  becomes  divided 

into   a   great  number    of    smaller 

cells,  in  each   of  which   a   single 

antherozoid  is  formed.     The  an- 

therozoids  are  like  those  of  Rock-  —SACHS. 


336.  Antheridial  branch. 


338.   Antheridium :  anther- 


CRYPTOGAMS  201 

weed  —  and  like  the  zoospores  of  many  Algse —  in  hav- 
ing two  cilia  for  locomotion. 

467.  The  archegonial  branches  bear  on  the  under  side 
at  the  base  of  the  rays  rows  of  flask-shaped  organs  called 
archegonia  (Fig.  334,  B).     In  the  archegonium  an  egg  cell 
(e)  is  situated  at  the  center  of  the  enlarged  basal  part. 
When  ready  for    fertilization  the  egg  may  be  reached 
through  the  canal  in  the  slender  portion,  or  neck,  of  the 
archegonium.    When  the  dew  is  on  the  plants  the  anthero- 
zoids  make  their  way  to  the  archegonial  branches  (which 
at  the  season  of  fertilization  are  not  much  grown),  and 
swarm  to  the  mouth  of  the  archegonia.     One  of  them 
passes  through  the  canal  and  fuses  with  the  egg  cell. 

468.  In  most  cases  of  oosporic  reproduction  in  Algse 
and  Fungi,  it  will  be  remembered,  the  oospore  falls  from 
the   parent   plant   before   it   germinates.      In   Nemalion, 
however,  fertilization  of  the  egg  gives  rise  to  a  structure 
organically  united  to  the  original  plant;    this  structure 
ultimately   bears   spores    (carpospores),   serving   to    dis- 
seminate the  species.      Marchantia  is   like  Nemalion   in 
the  noteworthy  fact  that  the  oospore  germinates  in  posi- 
tion, and   gives   rise  to   spores  only  after  an  interval  of 
growth  upon  the  parent  plant.     For  after  fertilization  the 
oospore  divides  into  two,  then  into  four,  then  into  eight 
parts,  and  so  on.     The  mass   of   cells  thus   originating 
grows  and   finally  forms  a  stalked   spore   capsule  (Fig. 
334,  c,  D),  or  sporogonium.     The  foot  of  the  sporogonium 
is  embedded  in  the  tissue  at  the  base  of  the  old  arche- 
gonium (ar). 

469.  The  spores  are  numerous,  free,  rounded  or  some- 
what angular,  walled  cells.     When  the  capsule  bursts,  one 
sees  that  it  contains  a  great  number  of  fine  threads  mixed 
with  the  spores.     They  have  the  property  of  twisting  and 
untwisting  with  changes  of  atmospheric  moisture,  and  so 
serve  to  give  the  spores  to  the  winds  from  time  to  time. 
From  the  spores  new  plants  develop. 

470.    The  archegonium  is  a  structure  that  is  found  in 
no  plant  lower  than  the  Liverworts.     As  we  go  upward, 


202 


CRYPTOGAMS 


however,  the  archegonium  appears  in  all  the  cryptogamic 
forms,  and  even  in  the  Gymnosperms  among  Flowering 
Plants.  In  Liverworts  and  all  plants  higher  in  the  vege- 
table series  the  fertilized  egg  cell  germinates  in  position, 
and  develops  to  a  spore-bearing  body. 

471.  Other  Liverworts.  —  Some  of  the  Liverworts  are  simpler  than 
Marchantia.     The  archegonia  and  antheridia  are  borne  by  the  thallus 

without  the  forma- 
tion of  special  erect 
branches.  The 
structure  of  the  spo- 
rogonium  (spore- 
bearing  body)  dif- 
fers widely  in  other 
339.  A  foliose  Liverwort.  members  of  the 

group  also.     Many 

of  the  species  —  e.g.  many  small  forms  found  on  tree  trunks  —  show  a 
distinction  of  stem  and  leaf  (Fig.  339).  Between  thalloid  and  leafy 
forms  gradations  are  found.  The  essential  structure  of  archegonium 
and  antheridium  is  the  same  throughout  the  group. 

472.  Mosses  are  closely  related  to  the  Liverworts.     The 
foliose  (leafy)  Liverworts  might  indeed  at  a  casual  glance 
be  mistaken  for  Mosses.      In   the   latter,    however,    the 
leaves  are  generally  arranged 

radially  about  the  stem  (Fig. 
340) ;  while  in  the  foliose  Liver- 
worts, as  seen  from  Fig.  339, 
the  leaves  are  so  disposed  that 
the  whole  shoot  has  a  flattened 
character  in  accordance  with 
the  creeping  habit. 

473.  The    Mosses    live    in 
ver}'  diverse  situations.     Some 
common   species  grow  wholly 
submerged  in  running   water 
like  Algae.     Again,  many  com- 
mon species  inhabit  extremely 
dry  places,  like  the  bare  face 

of  rocks,  where  there  is  no  soil  but  dust  and  debris  col- 
lected by  the  Mosses  themselves,  and  where  the  plants  can 


340.  A  Moss  shoot  after  the  pro- 
duction of  a  sporogonium : 
s,  spore  capsule ;  o,  opercu- 
lum ;  c,  calyptra. 


CRYPTOGAMS 


203 


have  water  only  when  dew  or  rain  falls.  Other  kinds  live 
in  the  crevices  of  bark  on  tree  trunks ;  others  on  soil.  The 
Sphagnum  Mosses  live  in  bogs,  of  which  they  sometimes 
form  the  chief  vegetation.  Peat  from 
these  bogs  (used  for  fuel  in  some  coun- 
tries) is  to  a  considerable  extent  made 
up  of  the  dead  stems  and  leaves  of  these 
Mosses. 

474.  Reproduction  is  essentially  the  same 
in  Mosses  as  in  Liverworts.  On  the  end 
of  the  stem,  usually, 
at  the  proper  sea- 
son archegonia  (Fig. 
341)  are  found.  An- 
theridia  (Fig.  342) 
arise  in  a  similar 


341. 


position ;  but  in 
most  species  the 
two  kinds  of  or- 

(/)  on  the  end  of  a  gans    OCCUr    on   dif- 
Moss  stem.  j?  i  mi 

terent  snoots.      Ine 


342.  Group  of  antheridia :  (a) 
and  sterile  filaments 


Archegonium 
of  a  Moss : 
e,  egg  cell; 
n,  neck;  I, 
lid  (opening 
before  fertil- 
ization) . 
—  SACHS. 


antlierozoid  is  motile  by  means  of  two  cilia,  and  reaches 
the  archegonium  and  finally  the  egg  cell  when  the  plants 
are  wet.  Fertilization 
results,  as  in  Liverworts, 
in  the  production  of  a 
(usually  long  -  stalked) 
sporogonium  (Fig.  340). 
The  upper  part  of  the  old 
archegonium  may  be  car- 
ried up  on  the  growing 
sporogonium  as  a  cap 
(calyptra,  c).  The  spore 
capsule  opens  for  libera- 
tion of  the  spores  by  the 

displacement   of    a   lid    (operculum,   o)   in  most   Mosses. 

475.    When  the  spore  germinates  it  gives  rise,  not  to  the 

Moss  shoot  directly,  but  to  a  many-branched  filamentous 


343.  Protonemaof  Moss:   b,  bud  of  Moss 
shoot.  —  FRANK. 


204 


CRYPTOGAMS 


growth  called  the  protonema,  which'  spreads  over  the  soil 
and  resembles  a  filamentous  Green  Alga.  Finally  shoots 
appear  as  buds  on  the  protonema  (Fig.  343). 

476.  It  will  be  noticed  that  in  the  Bryophytes  (Liver- 
worts and  Mosses)  the  fertilization  of  the  egg  cell  does 
not,  as  in  most  Algse,  produce  an  oospore  which  separates 
from  the  parent  and  develops  into  a   new  and   distinct 
plant.      The   fertilized   egg   remains   in   position   in   the 
archegonium  and  gives  rise  to  the  spore-producing  organ, 
or  sporogonium. 

FERNS   AND  FERN  ALLIES  (PTERIDOPHYTES) 

477.  Most  of  the  Ferns  and  Fern  allies  of  to-day  are 
comparatively  small  plants,   frequently  with  a  creeping 
habit;    some  grow  partly  or  wholly  submerged;    while 
several  small  species  are  floating  plants.     All  this  is  in 
strong  contrast  with  conditions  in  former  geological  times. 
In   the    Coal   period   Tree   Ferns    (now  confined  to  the 

tropics)  were  widely  distributed. 
Certain  relatives  of  the  modern 
slender,  creeping  Club  Mosses  (Fig. 
357)  were  trees  from  60  to  80  feet 
in  height.  Similarly  some  Equise- 
tumlike  plants,  now  represented 
mainly  by  species  from  1  to  4  or  5 
feet  tall  (Fig.  358)  were  tolerably 
stout  trees  30  feet  high.  Forests 
largely  composed  of  these  Crypto- 
gams formed  the  immense  coal  de- 
posits of  that  period. 

478.  Ferns  are  still  numerous,  and 
in  some  places  are  predominant  fea- 
tures of  the  vegetation.  In  the 
tropics  they  are  especially  abundant 

344.  A  tropical  Tree  Fern.    and  large  (Fig.  344).      In  most  com- 
mon species  the  stem  is  a  creeping 

rhizome  (Fig.  345),  wholly  or  partly  buried,  so  that  all 
that  one  sees  is  the  foliage  rising  from  the  ground.  Ferns 


CRYPTOGAMS 


205 


have  true  roots,  —  unlike  Mosses  and  Liverworts,  which 
are  attached  only  by  hairs,  or  rhizoids. 


34U.  Under  side  of  a  segment  of  Fern 
leaf,  showing  sori. 


345.  Rhizome  and  leaves  of  the 
Rock  Fern. 


347.  Section  of  sorus:  s,  sporangia; 
i,  indusium ;  6,  blade  of  the. 
leaf.  —  WOSSIDLO. 


479.  Spores  are  borne  in 
small  sporangia  (Fig.  348), 
clustered  in  groups  on  the 

under  sides  of  the  leaves  (Fig.  347).  Each  cluster,  or 
" fruit  spot"  (soms),  is  in  many  species  shielded  by  a 
membrane  (indusium,  i).  At  maturity,  and  on  the  occa- 
sion of  certain  conditions  of  moisture  in 
the  atmosphere,  the  sporangium  splits 
at  one  side.  The  top  is  slowly  thrown 
far  back,  and  then  suddenly  resumes  its 
former  place.  The 
spores  are  ejected  by 
the  violence  of  the 
motion. 

480.  The  germination  of  the  spore 
results  in  the  formation  of  a  small, 
thin,  heart-shaped  body  called  the 
protliallium  (Fig.  349),  in  shape  and 
habit  of  growth  much  resembling  a 
small  thalloid  Liverwort.  Prothallia  of  common  species 
are  from  a  quarter  to  a  half  inch  in  diameter,  and  may 


348.  A  sporangium. 


349.  Fern  prothallium: 
ar,  archegonia  ; 
an,  antheridia. 


206 


CRYPTOGAMS 


be  found  on  bare,  moist  earth  under  Ferns  ;  or,  better, 
in  greenhouses.  They  are  attached  to  the  soil  by  rhi- 
zoids,  most  of  which  spring  from  a  median  thickening,  the 
cushion.  On  the  under  surface,  mainly  nearer  the  more 
pointed  end  of  the  prothallium,  hemispherical  antheridia 
are  borne  (Fig.  350,  J9),  in  which  the  spiral,  ciliated 
antherozoids  (Fig.  350,  (7)  have  their  origin.  Archegonia 
(Fig.  350,  A)  may  be  found  on  the  same  prothallia,  nearer 

the  notched  (younger) 
extremity.  In  some  spe- 
cies, however,  antheridia 
and  archegonia  are  always 
borne  on  different  prothal- 
lia ;  though  the  spores 
from  which  the  two  sorts 
of  prothallia  arise  are 
indistinguishable . 

481.  ^Fertilization  of  the 

350.   A,  the  archegonium  with  egg  (e),  and  _  ^  ^^  ^^  ^^ 

prothallia    are    wet 


canal  (c) ;   B,  antheridium;    G,  an- 
therozoid, very  highly  magnified.—  the 

with  dew  or  rain,  by  the 

entrance  of  an  antherozoid  into  the  archegonium  and  the 
conjugation  of  antherozoid  and  egg  cell. 

482.  The  result  is  the  division  of  the  egg  and  the  for- 
mation of  an  embryonic  Fern  plant  (Fig.  351),  in  which 
the  beginnings  of  leaf,  stem,  and  root 

can  soon  be  made  out.  Commonly 
only  one  of  the  several  archegonia  which 
may  be  fertilized  gives  rise  to  a  per- 
fected Fern  plant.  After  the  establish- 
ment of  the  latter,  the  prothallium  dies. 

483.  The    entire   life   history  of  the 
Fern  thus  comprises   two    stages,  that 
of  the  prothallium  (bearing  archegonia 

and  antheridia),  and  that  of  the  leafy,    351.  prothallium  with 

spore-bearing  plant.    It  will  be  recalled 

that  in  some  of  the  lowest  Algae  (e.g. 

Vaucheria)  the  same  individual  plant  gives  rise  to  spores 


young     spore- 
bearing  plant. 


CRYPTOGAMS  207 

(zoospores)    germinating    without    fusion,    and    gametes 

destined  to  conjugate.     In  Ferns  it  is  plainly  seen  that 

the  two  sorts    of  reproductive  cells 

(spores  and  gametes)  are  not  borne 

at  the  same  period,  but  at  very  dif- 

ferent stages  of  the  life  cycle.     The 

two  stages  regularly  alternate.    This 

phenomenon  is  known  as  the  Alter- 

nation of  Generations.       That   form  ^   Section   trough   a 

very  young    Fern 

(stage    or   generation)  of  the  plant  plant:  s,  stem;  /, 

that  bears  gametes  (egg  cell,  anther-  leaf  ;  r,  root  ;  p,  the 

'  prothallmm;  a,  a, 

ozoid)  is  called  the  gametopliyte  ;  in  remains  of  arche- 


Ferns  the  prothallmm  is  the  gameto- 

phyte.     That   form    (stage   or   gen- 

eration) which  bears  spores  is  the  sporophyte;  in  Ferns 

the  leafy  plant  is  the  sporophyte. 

484.  The  Fern  prothallium  corresponds  to  the  thallus 
of  a  Liverwort  and  the  protonema  and  shoot  of  a  Moss  ; 
for  these  structures  all  bear  archegonia  and  antheridia. 
The  final  result  of  fertilization  in  Liverworts  and  Mosses 
is  a  sporogonium,  i.e.  a  spore-bearing  body.     The   final 
result   of   fertilization   in   Ferns   is   also  a  spore-bearing 
body  —  the  Fern  "  plant."    Sporogonium  and  Fern  "  plant  " 
have   the   same  origin  ;  they  are  therefore  of   the  same 
nature  :  both  are  sporophytes.     The  sporophyte  of  Liver- 
worts and  Mosses  (the  sporogonium)  has  no  root,  but  is, 
so  to  speak,  parasitic  on  the  parent  plant,  or  gametophyte. 
The  sporophyte  of  Ferns  has  a  root,  as  well  as  leaves,  and 
after  the  very  first  is  self-supporting.1 

485.  Selaginella  (Fig.  353)  is  usually  a  creeping  plant 
(a  common  species  is  ascending),  with  leaves  dorsiventrally 
arranged  ;  i.e.  so  placed  that  the  shoot  shows  an  upper  and 
an  under  side.     Special  branches  are  often  given  off  below, 
from  which  roots  are  sent  out.    The  sporangia  spring  from 

1  Alternation  of  generations  is  not  confined  to  Bryophytes  and  Pterido- 
phytes,  though  in  the  Pteridophytes  it  is  easier  to  see  than  elsewhere  in 
the  vegetable  kingdom.  It  is  foreshadowed  in  the  Thallophytes  and  occurs 
in  all  plants  above  them. 


208 


CRYPTOGAMS 


leaf  axils  in  the  terminal  "fruiting  spikes  "  (Fig.  354). 
They  are  of  two  kinds  as  concerns  contents,  and  often  as 


353.  Selaginella. 

concerns  size  and  color.  The  larger  (macrosporanyia,  ma, 
Fig.  354)  each  contain  four  large  spores,  or  macrospores ; 
the  smaller  (microsporangia,  mi)  con- 
tain large  numbers  of  very  much 
smaller  microspores.  Macrosporangia 
are  found  only  in  lower  axils,  or  else 
only  in  axils  on  one  side  of  the  spike. 
Leaves  with  which 
sporangia  occur,  as 
here,  are  termed 
sporophylls. 

486.  In  the  af- 
ter development  of 
the  spores  Selagi- 
nella departs  in  a 
remarkable  man- 
ner from  the  Ferns.  The  spores  of 
Ferns  give  rise  to  distinct  structures 
(prothallia)  upon  which  archegonia 
and  antheridia  are  produced.  In 
Selaginella  the  germination  of  the 
spore  goes  no  farther  than  the  formation  of  a  number  of 
cells  within  the  original  spore  walls.  Moreover,  the  nature 
of  these  internal  formations  is  different  in  the  two  kinds 


ma- 


..mi 


355.  Section  of  micro- 
spore:  s,  cells 
in  which  an- 
therozoids  ori- 
ginate; p,  pro- 
thallial  cell. 


354. 


Fruiting  spike  of 
Selaginella  (/), 
and  the  same  in 
section  magni- 
fied :  ma,  macro- 
sporangium  ;  mi, 
microsporangium. 
—  GOEBEL. 


CRYPTOGAMS  209 

of   Selaginella  spores.       In    the    microspore   these    cells, 

filling  the  whole  interior,  compose  an  antheridium,  with 

only    the    slightest    rudiment    of    a    prothallium  ;     and 

within    this   antheridial  body   are  formed   antherozoids. 

In  the  macrospore  a  reduced  prothallium  appears.     This 

finally  increases  sufficiently   to  burst 

open  the  spore  at  one  end  (Fig.  356)  ; 

and  on   the  exposed    surface    several 

archegonia     develop.          Fertilization 

takes    place    after    the     spores    have 

fallen  to  the   ground,  when  water  is 

present  to  allow  the  antherozoids  to 

make   their   way   to   the    archegonia. 

Then,  as  in  Ferns,  an  embryonic  plant 

is  formed,  which  soon  develops  stem,    ***•   The  . 

with  prothallium 
root,  and  leaves.  (p)    bearing    ar- 


487.  Two  points  are  to  be  particu- 

larly  noted  with  regard  to  the  repro-  tion. 

duction  of  Selaginella  : 

(1)  Spores  are  of  two  kinds  as  regards  (a)  origin,  (6)  size, 
(c)  ultimate  development.     For  they  originate  in  different 
kinds   of  sporangia,  are  very  unequal  in  size,  and  give 
rise  to  antheridia  and  archegonia,  respectively.    This  con- 
dition is  foreshadowed  in  the  Ferns,  of  which  some  species 
have  two  sorts  of  prothallia  (§  480).     Here  (in  Selaginella) 
the  differentiation  extends  to  the  spores  and  sporangia. 

(2)  The  gametophyte  (prothallial  structure)  is  reduced 
so  much  that  it  is  held  in  the  original  spore  walls,  and  has 
lost  all  independence,  possessing  neither  chlorophyll  nor 
rhizoids. 

488.  Other    Pteridophytes   which   one   will    frequently 
see  are  Lycopodium,  the  Club  Moss,  and  JEquisetum,  the 
Scouring  Rush  or  Horsetail. 

489.  Lycopodium  (Fig.  357),  to  be  met  with  in  woods 
and  old  pastures  and  in  partly  shaded  situations,  resem- 
bles Selaginella  in  general  habit,  except  that  the  leaves  are 
usually  arranged  radially.     The  rhizome  runs  close  to  the 
ground  or  in  the  soil,  and  sends  up  erect  branches.     Spo- 

OUT.    OF    EOT.  -  14 


210 


CRYPTOGAMS 


rangia,  all  of  one  sort,  are  borne  in  leaf  axils  (s,  Fig.  357). 
The  sporangia!  leaves  are  usually  grouped  apart  in  a  "  fruit- 
ing "  spike.  Spores  are  of  one 
kind,  and  give  rise  to  prothallia 
which  in  many  species  are  fleshy, 
tuberculate  bodies,  leading  a  more 
or  less  subterranean  existence. 
Fertilization  and  the  growth  of 
the  sporophyte  have  much  the 
same  history  as  in  Ferns. 

490.  Equisetum,  the  Horsetail, 
or  Scouring  Rush  (Fig.  358), 
grows  preferably  in 
sandy  soil,  and  often 
in  moist  situations. 
One  of  the  common- 
est species  is  to  be 
found  along  railroad 
banks.  The  north- 
ern species  are,  in 
general,  a  foot  or  so 
tall,  though  in  the 
spo-  tropics  Equisetum 
giganteum,  a  slen- 


357.  Lycopodium:  /,  fruiting  portion; 
rangium  in  axil  of  a  sporophyll. 


der,  clambering  species,  reaches  a  height  of  thirty  feet. 

491.  The  upright  shoots  spring  from  a  running  base. 
The  stem  is  clothed  at  the  nodes  by  short  sheaths  of  con- 
joined scaly  leaves.      When  branches  arise  they  spring 
from  the  nodes   and   display  the   same   arrangement   of 
reduced  foliage  (Fig.  358). 

492.  The  terminal  portion  of  fertile  shoots  is  converted 
into  a  spore-bearing  region  (/),  in  which  the  leaves  are 
peculiarly  modified  (Fig.  358,  B,  C).     They  are  peltate  in 
form,  and  bear  on  the   under  (or  inner)  side  pocketlike 
sporangia  projecting  toward  the  stem.      The  spores  are 
very  numerous.     Each  one  is  provided  with  two  narrow 
strips  of  membrane  (called  elaters,  Fig.  358,  2>),  fastened 
to  the  spore  at  their  middle  points,  the  four  extremities 


CRYPTOGAMS 


211 


extending  like  arms  when  dry,  but  curling  up  suddenly 
when  moistened  by  water  or  damp  air.  If  a  lot  of  the 
dry  spores  under  the  microscope 
is  gently  breathed  upon,  it  is  seen 
that  the  elaters  almost  instantly 
curl ;  and  in  doing  so  the  elaters 
of  neighboring  spores  become  en- 
tangled, so  that  the  hitherto  dust- 
like  heap  becomes  a  coherent  fluffy 
mass.  This  entanglement  of  the 
spores  is  of  importance  in  the 
economy  of  the  plant,  from  the 
fact  that  the  prothallia  to  which 
they  give  rise  are  of  two  kinds. 
One  kind  bears  archegonia  alone, 
the  other  only  antheridia.  If 
archegonial  and  antheridial  pro- 
thallia were  separated,  evidently  353,  EquisetUm:  A,  a  shoot 

fertilization    of    the    egg    Cells    by  bearing  a  fruiting  cone 

, ,  .  -,  (/) ;  B,  axis  and  spo- 

the   antherozoids    could  not  take  lophylls  of  the  cone- 

place,  and  new  Equiseturn  plants  G>  sectional  view  of  a 

•i-i.i  i          T       mi  sporophyll;  D.  a  spore. 

would  not  be  produced.    The  pro- 

thallium  and  its  organs  are  so  much  like  corresponding 
structures  in  Ferns  that  no  separate  description  need  be 
given  here. 

Relationship  of  Cryptogams  and  Phanerogams. — Suppose  in  the  ma- 
crosporangium  of  Selaginella  only  one  macrospore  were  to  mature ; 
that  this  macrospore  were  to  remain  permanently  in  the  sporangium ; 
that  the  prothalliuin  were  to  be  still  further  reduced,  so  as  not  to  burst 
the  macrospore  wall ;  that  the  microspore  should  be  brought  to  the 
macrosporangium,  and  put  out  a  tube,  which,  penetrating  into  the 
macrospore,  should  conduct  the  antherozoids  to  the  archegonia;  and 
that  the  resulting  Selaginella  plant  should  develop  and  form  its  first 
pair  of  leaves  quite  within  the  macrospore, — then  we  should  have 
an  arrangement  very  like  what  actually  exists  in  ovule,  pollen,  and 
seed  in  Flowering  Plants.  The  embryo  sac  of  Phanerogams  is 
regarded  as  a  macrospore  remaining  in  its  sporangium  (nucellus  of 
ovule,  the  integuments  representing  the  indusia  of  some  Pterido- 
phytes).  The  several  nuclei  of  the  sac  probably  represent  cells  of  a 
reduced  prothalliurn,  the  egg  cell  standing  for  the  egg  cell  of  an  arche- 


D 


212      MINUTE  ANATOMY   OF  FLOWERING  PLANTS 

gonium.  In  the  embryo  sac  of  Gymnosperms  (Conifers,  etc.)  a  defi- 
nite prothallial  tissue  is  formed  with  rudimentary  archegonia  at  the 
summit. 

The  pollen  grain  of  Phanerogams  corresponds  to  the  microspore 
of  Selaginella.  At  the  time  of  fertilization  there  are  three  or  more 
cells  in  the  pollen  grain  and  tube.  These  cells  —  like  those  in  the 
developed  microspore  of  Selaginella  —  are  regarded  as  prothallial  in 
character,  two  of  them  (those  which  pass  through  the  pollen  tube  to 
the  embryo  sac)  being  equivalent  to  antherozoids.  In  some  Gymno- 
sperms the  fertilizing  bodies  from  the  pollen  are  motile,  like  the  an- 
therozoids of  Pteridophytes. 

Thus  the  gametophyte  of  Flowering  Plants  is  wholly  within  embryo 
sac  and  pollen  grain.  In  Liverworts  the  gametophyte  (vegetative 
thallus)  is  larger  than  the  sporophyte  (sporogonium).  In  Ferns  the 
proportions  of  the  alternating  generations  are  reversed,  the  gameto- 
phyte being  much  the  smaller.  In  Flowering  Plants  reduction  of 
gametophyte  and  increase  of  sporophyte  have  been  carried  to  an 
extreme.  The  carpels  and  stamens  of  Phanerogams  are  the  spore- 
bearing  leaves,  ovules  (or  their  nucelli)  and  pollen  sacs  being  spo- 
rangia ;  carpels  and  stamens  are  therefore  often  termed  sporopliylls. 


XVII.    THE  MINUTE  ANATOMY  OP   FLOWERING 

PLANTS 

493.  Cellular  structure.  —  Attention  has  already  been 
called,  incidentally,  in  several  places,  to  the  fact  that  plants 
are  made  up  of  definite  members  of  small  size,  called  cells. 
All  new  cells  are  formed  from  preexisting  cells.     Com- 
monly this   comes   about  by  division :    the  original  cell 
divides  to  form  two  or  more,  each  of  which  may  increase 
by  independent  growth,  and  in  turn  give  rise  by  division 
to  new  cells.     The  very  first  cell  of  the  embryo  has  a 
different  origin,  however.     In  fertilization,  a  nucleus  from 
the   pollen  tube,  entering  the  embryo  sac  of   the  ovule, 
fuses  with  a  nucleus  there  found  (see  Fig.  164).     As  the 
result  of  this  union  the  initial  cell  of  the  new  plant  is 
formed  within  the  embryo  sac.     All  future  increase  pro- 
ceeds by  division  and  independent  growth. 

494.  The  cell,  then,  is  the  unit  of  plant   structure. — 
It  is  the  unit  also  of  plant  activity.     Whatever  activities 
the  plant  as  a  whole  manifests  —  such  as  growth,  move- 


MINUTE  ANATOMY  OF  FLOWERING  PLANTS     213 


ment,  absorption  of  food  material,  assimilation  —  these 
activities  are  carried  on  by  the  cooperation  of  the  cells 
composing  the  plant.  This  being  the  case,  it  is  important 
to  know  something  of  the  structure  of  the  typical  vege- 
table cell. 

495.  Structure  of  the  cell. —In  illustration  of  the 
typical  vegetable  cell,  we  might  select  cells  from  the  apex 
of  a  growing  stem  or  root, 
or  from  a  leaf  rudiment,  or 
from  the  young,  growing 
fruit.  Thin  sections  cut 
from  any  of  these  regions 
would  show,  under  the  com- 


pound micro- 
scope, the 
cells  as  sev- 
eral angled, 


359.  Sectional  view  of  young  cells  from 


the  root  tip. 

thin  -  walled   components    of     the    tissue 
(Fig.  359). 

496.  The  living  substance  of  the  cell  is 
protoplasm.  It  has  been  described  as  being 
of  a  jellylike  consistency.  A  better  illus- 
tration of  the  semifluid,  yet  cohesive,  prop- 
erties of  protoplasm  is  afforded  by  the  raw 
white  of  egg.  The  fluidity  varies  in  differ- 
ent portions  of  the  protoplasmic  body  of  the 
cell,  some  parts  being  relatively  firm,  oth- 
ers containing  a  very  large  percentage  of 
water,  and  being,  therefore,  capable  of 
stiii'o-in ••  hair  more  or  less  rapid  movement  in  circulating 
of  a  Nettie,  currents.  In  some  cells  in  which  the  nu- 
terminal  cleus  ^s  suspended  near  the  center  by 
cell  the  cir-  threads  of  protoplasm  (Fig.  360),  the  cur- 

culation  of  ,  •,        , , 

protoplasm  rents  may  be  seen  in  the  threads,  passing 

is  indicated  toward  and  away  from  the  nucleus.     Two 

opposite  currents  may  often  be  observed  in 

the  same  thread.     In  cells  like  the  largest  one  of  Fig. 

362    the    whole    body    of   protoplasm,    except    that   part 


214      MINUTE  ANATOMY  OF  FLOWERING  PLANTS 


directly  in  contact  with  the  walls,  may  be  in  slow  rota- 
tion, dragging  with  it  the  nucleus. l 

497.  The  term  protoplasm  includes  all  the  living  constit- 
uents of  the  cell.  "  The  word  protoplasm  is  a  morpho- 
logical term.  .  .  .  Protoplasm  is  not  a  single  chemical 
substance,  however  complex  in  composition,  but  is  com- 
posed of  a  large  number  of  different  chemical  substances, 
which  we  have  to  picture  to  ourselves  as  most  minute 
particles,  united  together  to  form  a  wonderfully  complex 
structure.  ...  In  this  mixture  of  substances,  the  wonder- 
ful vital  phenomena  may  very  frequently  be  observed 
(contractility,  irritability,  etc.)."  2 

Of  the  protoplasmic  cell  contents  we  have  to  distinguish 
a  rounded  central  body,  the  nucleus  (Figs.  359,  362,  n),  in 

many  young  cells  occupying  a 
considerable  portion  of  the  cell 
space;  and  the  general  mass, 
aside  from  the  nucleus,  called 
the  cytoplasm. 

The  nucleus  is  denser  than 
the  cytoplasm.  It  is  made  up 
of  definite  parts,  differing  in 
chemical  constitution,  definitely 
arranged.  Although  actually 
of  extremely  small  size,  the  nu- 
cleus is  a  highly  organized 
body.  It  is  the  controlling  part 
of  the  cell.  It  is  the  first  part 
to  divide  when  new  cells  are  to 
be  formed,  and  in  division 
passes  through  a  complicated 
series  of  changes  (Fig.  361),  by 
which  equal  shares  in  all  the  essential  constituents  of  the 


Nuclear  and  cell  division : 
A,B,C,  successive  stages ; 
n,  region  of  the  nucleus; 
c,  cytoplasm  ;  d,  d,  begin- 
nings of  daughter  nuclei. 
In  C,  the  original  cell  has 
become  divided  internally 
into  two,  each  with  a  large 
nucleus  (n). 

—  GUIGNARD. 


1  Stamen  hairs  of  Tradescantia,  cells  of  the  leaf  of  Elodea  canadensis 
or  of  Vallisneria  spiralis,  and  cells  of  Stonewort  (CTmra),  are  objects  in 
which  movements  of  protoplasm  may  be  studied.  See  Goodale,  Ch.  VI.  j 
Strasburger,  p.  244. 

2O.  Hertwig,  "The  Cell,"  p.  13. 


MINUTE  AN  ATOM  T  OF  FLOWERING   PLANTS      215 

parent  nucleus  are  assured  to  the  two  resulting  nuclei. 
Only  after  the  nucleus  of  a  cell  has  finished  its  division, 
is  the  surrounding  cytoplasm  separated  into  two  portions. 
The  production  of  two  cells  from  one  is  completed  by  the 
formation  of  a  new  transverse  wall. 

498.  Many  cells  possess,  in  addition  to  the  nucleus,  pro- 
toplasmic organs  performing  special  offices  in  the  general 
work  of  the  cell.  Cells  from  the  interior  of  the  leaf,  for 
example  Fig.  382,  contain  numerous  rounded  or  lens- 
shaped  bodies,  lying  in  the  cytoplasm  near  the  walls. 
These  bodies,  colored  green  by  the  chlorophyll  pigment 
which  they  contain,  are  the 
chlorophyll  granules  or  chlo- 
roplastids.  They  give  plants 
their  characteristic  green 
color.  They  are  active  in 
carbon  assimilation.  Simi- 
lar cell  organs,  with  red 
or  yellow  pigment  instead 
of  green,  give  color  to 
fruits  and  flowers.  They 
are  called  chromoplastids. 

A  thin  external  layer  of 
the  cytoplasm  next  the  cell 
wall  may  be  distinguished 
by  its  superior  clearness  and 
the  absence  of  granulation. 
It  is  very  probable  that  this 
really  constitutes  a  sort  of 
membrane,  possessing  a  closeness  of  structure  and  tenacity 
above  that  of  the  rest  of  the  cytoplasm.  The  remainder 
of  the  cytoplasm  is  highly  granular  in  appearance,  owing 
chiefly  to  the  varying  density  of  the  protoplasm  itself. 
Except  in  their  earliest  stages  active  cells  contain  inter- 
spaces, or  vacuoles,  filled  with  water  and  dissolved  sub- 
stances (Fig.  362).  One  large  vacuole  may  fill  the 
greater  part  of  the  cell,  the  protoplasm  forming  a  layer 
next  the  wall.  The  watery  contents  of  the  vacuole  or 


216      MINUTE  ANATOMY  OF  FLOWERING  PLANTS 


vacuoles  is  the  cell  sap.  It  is  sometimes  colored.  The 
red  and  yellow  colors  of  healthy  leaves  are  generally  due 
to  colored  cell  sap  in  some  of  the  cells,  masking  the 
green  of  the  chlorophyll  granules.  Bright  colors  of  fruits 
and  flowers  also  are  generally  due  partly  to  colored  cell 
sap.  The  cell  sap  may  contain  sugar  in  storage,  as  it  does 
in  the  root  of  the  sugar  beet  and  in  the  stem  of  the  sugar 
cane. 

Certain  substances  belonging  to  the  class  of  formed  mat- 
ters (non-protoplasmic)  are  of   such  frequent  occurrence 
and  are  produced    in  masses  of  such 
size  in  the  cell   that  they  should  be 
briefly  described. 

499.  Starch.  —  Starch  is  the  form 
in  which  elaborated  plant  food  is  most 
commonly  stored.  It  is  laid  down  in 
the  cells  of  storage  organs,  e.g.  tubers, 
in  rounded  granules  (Fig.  363).  When 
these  are  considerably  magnified  they 
are  seen  to  be  stratified,  in  evidence  of 
the  mode  of  deposition  of  the  starch  in  successive  layers. 
If  the  granules  are 
closely  packed  to- 
gether, they  may 
become  angular  in- 
stead of  rounded. 

500.  Protein  gran- 
ules and  crystals.  — 
The  external  stor- 
age cells  of  wheat 
grains  afford  exam- 
ples of  protein  gran- 
ules (Fig.  364).  The 

Contents  of  these  364.  Transverse  section  near  the  outside  of  a  Wheat 
Cells  make  Up  the  grain  :  «,  the  husk  (pericarp,  integuments) ; 

,,     ,  6,  cells  with  protein  granules;    c,  starch 

SO-Called    gluten    of  cells. -TSCHIRCH. 

1  Protein  is  the  name  given  to  organic  substance,  whether  of  animal  or 
of  vegetable  origin,  containing  nitrogen  and  a  small  proportion  of  other 


363.   Starch  cells  from 
Potato  tuber. 


MINUTE  ANATOMY  OF  FLOWERING  PLANTS      217 


I— J 


wheat,  which  is,  or  should  be,  a  highly  nutritious  element 
of  wheat  flour.  In  the  cells  of  the  potato  tuber  are  to  be 
found  examples  of  proteid  matter  formed 
into  cubical  crystals.  These  granules  and 
crystals  are  storage  forms  of  protein. 

501.  Crystals   of    calcium  compounds  — 
calcic  carbonate  and  oxalate  —  are  of  very 
common  occurrence  (Fig.  365).  These  are 
generally  considered  to  be  waste  products 
of  the  chemical  changes  going  on  in  the 
cells.1     Other    substances    also  occur    in 
crystalline  form,  but  less  frequently. 

502.  The  account  here  given  of  the  typi- 
cal vegetable  cell,  as  regards  protoplasmic 
structures  and  cell  contents,  is  of  course 

brief  and  incomplete;  it  is  meant  to  be  355.  ceils  contain- 
suggestive  of  the  extent  of  the  subject.  in&  «eedie- 

rm  c  1-11  like  crystals 

Ihe  nature  01  the  cell  has  been,  and  will  (raphides)of 

long  continue   to   be,    the   object   of    the 
investigations  of  numerous  workers. 

503.  Certain  cells  of  certain  plants  regularly  contain 
more  than  one  nucleus  each.     And  in  not  a  few  of  the 
lower  cryptogams  great  numbers  of  nuclei  exist  within 
a   common  wall.     The    many-branched   plant   body  may 
in  such  cases  consist  of  one  continuous  chamber  without 
internal  division  walls.     Each  nucleus  represents  a  single 
cell,  but  there  is  no  corresponding  division  of  the  cyto- 
plasm. 

504.  The   cell  wall.  —  Early  investigators  assigned  to 
the  cell  wall  the  chief  importance ;  but  we  now  know  that 
life   resides   in   the  protoplasm,   and  that  the  wall  is  of 
secondary  importance.     In  many  of  the  lower  plants  the 
contents   of   certain   reproductive  cells  break  from  their 
walls,  and  swim  freely  forth  (Fig.   285).     Only  after  a 

matters  in  addition  to  the  carbon,  hydrogen,  and  oxygen  which  compose 
starch  and  sugar.  Proteid  substances  enter  directly,  and  as  such,  into 
the  composition  of  protoplasm. 

1  It  is  quite  possible  that  calcium  oxalate  is  a  storage  form  of  food. 


calcium  oxa- 
late. 


218      MINUTE  ANATOMY  OF  FLOWERING  PLANTS 


period  of  active  locomotion  do  they  settle  down  and 
become  invested  with  a  membrane.  This  fact,  among 
others,  shows  the  essential  independence  of  protoplasm  in 
cells,  and  the  subordinate  role  of  the  wall. 

The  wall  is  a  product  of  the  protoplasm.  New  walls 
are  formed  by  the  conversion  of  a  portion  of  the  proto^ 
plasm  into  the  substance  of  the  wall.  In 
young  cells,  and  many  old  cells,  this  sub- 
stance is  cellulose,  chemically  resembling 
starch.  It  is  a  regular  occurrence  that 
in  certain  of  the  cells  of  the  plant  body, 
the  protoplasm  becomes  at  length  wholly 
converted  into  wall,  when,  of  course,  the 
life  of  these  particular  cells  is  at  an  end. 
In  the  later  phases  of  this  process,  the 
depositions  may  take  a  form  differing 
chemically  from  cellulose.  We  have,  for 
instance,  in  wood  cells,  lignified  walls;  in 
cork  cells,  walls  containing  a  fatty  sub- 
stance called  suberin.  Modified  walls  of 
these  sorts  have  physical  properties  differ- 
ing from  those  of  cellulose.  For  exam- 
ple, the  suberized  walls  of  cork  resist  the 
entrance  of  water,  whereas  the  cellulose 
366.  Wood  fibers  in  of  pith  and  the  lignified  walls  of  wood 
take  water  into  their  pores  readily. 

Walls   are    seldom,    or    never,    evenly 
face  v'ieTof    thickened  when  the  depositions  are  con- 
pits;    6,  the    siderable,  but  certain  areas  remain  thin, 
pitsinsection.    eyen  ftfter  the  completion  of  the  thicken- 
ing process.     Or  the  greater  part  of  the  cell  wall  may  fail 
to  thicken,   and  then  the  depositions  take  the   form  of 
raised  markings  on  the  interior  of  the  walls.     Examples 
are  the  annular  and  spiral  ducts  (Fig.  371). 

505.  Changes  in  the  shape  of  the  cell. —  The'cells  of  the 
growing  tips  of  the  stem  and  root,  and  young  and  actively 
dividing  cells  elsewhere,  are,  in  general,  nearly  isodiamet- 
rical.  Subsequently,  many  of  these  cells  become  greatly 


longitudinal 
section:  a, 
part  of  the 


MINUTE  ANATOMY  OF  FLOWERING  PLANTS     219 


changed  in  shape.  Cells  of  the  external  layer  are  in 
many  instances  flattened,  in  accordance  with  their  protec- 
tive function.  Cells  of  strengthening  and  conducting 
tissues,  on  the  other  hand,  are  frequently  greatly  elon- 
gated. In  the  conducting  tissues,  elongated  cells  placed 
end  to  end  in  rows  become  united  into  tubes  or  ducts, 
the  end  walls  being  absorbed,  wholly  or  in  part,  to  allow 
the  passage  of  liquids. 

506.  Several  of  the  principal  modifications  of  cells  should 
now  be  described.     We  may  begin  with 

wood  fibers. 

507.  Wood,  whether   occurring    in    so- 
called  woody  stems,  or  in  succulent  herba- 
ceous   stems,  consists    largely  of    fibrous 
cells,  associated,  in  most  cases,  with  ducts, 
or  vessels.     The  fibrous  cells  are  of  a  great 
variety  of  form  and  appearance  in  differ- 
ent plants  ;  but  those  which  are  termed, 
in  rather   an  indefinite  way,  wood  fibers, 
are    pointed    cells,    several    times    longer 
than  broad,  having  thickened  and  lignified 
walls,  and   characteristically   showing   in 
these  walls  numerous  pits,  i.e.  spots  where 
the  walls  have  remained  thin  or  become 
perforated  in  such  a  way  as  to  allow  com- 
munication between  the  cells  (Fig.  366). 

508.  Bast  fibers.  —  These  are  found  in 
strands  in  the  bark.     They  are  generally 

of  considerable  length,  compared  with  their  diameters. 
Their  walls  are  generally  much  thickened,  so  that  the 
internal  space,  or  lumen,  is  small,  as  seen  in  cross  section 
(Fig.  367).  Bast  fibers  give  strength  to  the  inner,  stringy 
bark  of  the  Basswood,  the  Grapevine,  the  Leatherwood, 
and  so  on.  They  constitute  the  fiber  of  Flax,  from  which 
linen  fabric  is  woven. 

509.  Collenchyma.  —  The  name  collenchyma  is  given  to 
masses    of    cylindrical   or   prismatic    cells,    having   walls 
thickened  at  the  corners  in  a  peculiar  manner  (Figs.  368, 


220      MINUTE  ANATOMY  OF  FLOWERING  PLANTS 


308.  Cross  section  of 
collenchyma. 


369).      These  walls,  when  seen  in  cross  section,  have  a 
distinctive  glistening  ap- 
pearance.     Collenchyma 

—  tissue     composed     of 
such  collenchymatous  cells 

—  is  one  kind  of  strength- 
ening tissue.     It  is  to  be 
found    near    the    surface 
of  herbaceous   stems,    of 

petioles,  and  of  leaves,  along  the  midribs. 
510.  Grit  cells,  or  sclerotic  cells,  with  very 

mucli  thickened  hard  walls,  are  exemplified 

in  the  rind  and  external  flesh  of  the  pear, 

where  they  occur  in  groups.     The   walls 

are  traversed  by  canals,  of  the  same  nature 

as  the  pits  spoken  of  above  (Fig.  370). 

Shells  of  nuts  also 
give  good  illus- 
trations of  cells 
with  walls  simi- 
larly thickened, 
and  affording  pro- 


W:^ 


Q 
P 

k 

?~ 


Grit  cells  from  a  pear. 


369.  Longitudinal 
section  of 
collenchyma. 
The  lens- 
shaped  bod- 
ies are  chlo- 
rophyll gran- 
ules. 

tection  by  consequent  firmness. 
511.  Cell  union,  or  fusion,  is 
illustrated  in  the  case  of  many  ducts,  in  which 
it  is  impossible  to  distinguish  the  original  cells, 
placed  end  to  end.  The  ducts  of  the  wood  are 
tubes  giving  unbroken  communication  between 
the  absorbent  roots  and  the  leaves.  The  walls 
may  remain  relatively  thin ;  in  this  case  they  are 
braced  internally  by  rings  or  spiral  thickenings 
(Fig.  371).  The  ducts  take  their  names  from 
their  markings,  being  designated  as  annular,  spi- 
ral, or  pitted  ducts,  etc. 

512.  Milk  tubes,  or,  in  more  technical  lan- 
guage, latex  tubes,  holding  the  milky  juice  of  Poppies, 
Dandelions,  and  allied  plants,  are  formed  from  originally 
distinct  cells  by  the  breaking  down  of  intervening  walls 


371.  Spiral 
duct. 


MINUTE  ANATOMY  OF  FLOWERING   PLANTS     221 


372.   Latex  tubes  (J). 

—  TSCHIBCH. 


(Fig.  372).  The  cell  fusions  may  take  place  mainly  in 
longitudinal  directions,  giving  the 
semblance  of  jointed  tubes,  or  in  all 
directions,  producing  a  dense  net- 
work. In  the  Milkweeds  and  the 
Euphorbias  the  milky  juice  (latex) 
is  held  in  elongated,  branching, 
tubular  sacs  originating  as  single 
cells  in  the  embryo,  and  growing 
with  the  growth  of  the  plant  until 
they  have  pushed  their  way  into 
every  part  of  the  plant  body.  The 
latex  itself  is  a  mixture  of  a  con- 
siderable variety  of  substances; 
sometimes  some  of  the  ingredients 
are  poisonous,  as,  for  example,  mor- 
phia, the  active  principle  of  opium,  found  in  the  latex 
of  the  Poppy. 

513.  Tissues.  —  The  word  tissue  has  been   frequently 
used  above  without  exact  definition,  yet  probably  without 
misapprehension.      Technically  the  term  tissue  means  a 
mass  or  collection  of  cells  of  the  same  kind.     Any  num- 
ber of  cells  of  a  certain  kind  constitute  a  particular  kind 
of  tissue.     Thus  collenchyma,  a  particular  kind  of  tissue, 
was  described  above. 

514.  Fibrovascular  bundles  are  so  called  from  the  fact 
that  they  are  made  up  largely  of  fibrous  cells  and  vessels 
(ducts).     In  a  translucent  herbaceous  stem  like  that  of 
the  Balsam,  the  bundles  may  be  seen  without  dissection, 
as  strands  lying  not  far  beneath  the  surface,  traversing  the 
entire  length  of  the  stem,  and  giving  off  branches  to  the 
leaves.     In  the  cross  section  of  such  a  stem  these  bundles 
would   be    seen    as    several  —  perhaps   five  —  areas   more 
opaque  than  the  surrounding  parenchyma,  arranged  ap- 
proximately in  a  circle  (compare  Fig.  376).     Upon  exami- 
nation with  a  proper  power  of  the  microscope  each  bundle 
would  be  seen  to  consist  of  three  parts  (Fig.  373).     The 
inner  of  these  consists  largely  of  wood  fibers  and  ducts. 


222     MINUTE  ANATOMY  OF  FLOWERING  PLANTS 


373.  Fibrovascular  bundle  of  a  Di- 
cotyledon :  ph,  phloem  ;  c, 
cambium ;  d,  duct,  and  /, 
fibers  of  the  xylem. 


It  is  called  the  xylem  or  wood  portion.     The  outer  con- 
tains  more    rounded    cells,   but  typically   possesses   bast 

fibers  in  groups,  and  scat- 
tered tubes.  It  is  called 
the  phloem.  Between  xylem 
and  phloem  is  a  region  occu- 
pied by  thin-walled  formative 
tissue,  from  which,  by  cell 
division,  growth,  and  modi- 
fication, all  the  elements  of 
both  xylem  and  phloem  are 
derived.  It  is  called  the  cam- 
bium. The  cambium,  during 
the  active  growth  of  the  stem, 
continuously  forms  xylem  on 
one  side,  phloem  on  the  other. 
The  outside  of  the  xylem  is  thus  the  newest,  while  the 
innermost  parts  of  phloem  are  the  newest.  In  old,  woody 
stems,  where  the  number  of  bundlesjsancr eased,  and  they 
are  crowded  together,  the  cam^ji^^S^ffie^sev^ral  bundles 
are  continuous  around  th 
stem,  forming  a  thin  sheat 
outside  the  wood.  It  is  at 
the  cambium  that  the  bark 
of  twigs,  especially  in  spring 
when  growth  is  most  active, 
may  easily  be  separated  from 
the  wood.  The  phloem  is 
then,  of  course,  removed  with 
the  bark,  of  which  it  forms 
the  inner  part. 

515.  Fibrovascular  bun- 
dles of  the  sort  described  in- 
crease in  thickness  from  year 
to  year,  if  the  plant  is  a 
perennial.  They  are  found  in  dicotyledons.  The  charac- 
teristic bundle  of  the  monocotyledons  lacks  the  cambium 
(Fig.  374).  The  xylem  also  is  much  reduced.  Each 


374.  Monocotyledonous  fibrovascu- 
lar  bundle :  ph,  phloem ;  d, 
duct  (xylem) ;  p,  pith  cell. 


MINUTE  ANATOMY  OF  FLOWERING  PLANTS      228 

bundle  is  surrounded  by  a  sheath  of  thick-walled  lignified 
tissue,  to  which  it  largely  owes  its  tensile  strength.  Once 
formed  from  the  general  formative  tissue  of  the  stem, 
the  bundle  shows  no  further  growth,  no  annual  increase 
of  xylem  and  phloem. 


STRUCTURE  OF  STEMS 

516.  On   one   or  the  other  of  two  types  the  stems  of 
phanerogamous  plants  are  constructed.     In  one,  the  wood 
is  made  up  of  separate  bundles,  scattered  here  and  there 
throughout  the  whole  diameter  of  the  stem.     In  the  other, 
the  wood  is  all  collected  to  form  a  layer  between  a  central 
cellular  part  which  has  none  in  it,  the  pith,  and  an  outer 
cellular  part,  the  bark. 

517.  An  Asparagus  shoot  and  a  Cornstalk  for  herbs, 
and   a   Rattan   for   a   woody   kind,   represent   the    first. 
To    it    belong    all    monocotyledons.      A 

Beanstalk  and  the  stem  of  any  common 
shrub  or  tree  represent  the  second;  and 
to  it  belong  all  plants  with  dicotyledon- 
ous or  polycotyledonous  embryo.  The 
first  has  been  called,  not  very  properly, 
endogenous,  which  means  inside  grow- 
ing ;  the  second,  properly  enough,  exo- 
genous, or  outside  growing. 

518.  Endogenous  stems,  those  of  mono- 
cotyledons, attain  their  greatest  size  and    375.  structure  of  a 

,  .    . .      ,         ,  ,  •      T»   i  Cornstalk,  in 

most  characteristic  development  in  .r  alms 
and  Dragon  trees.  A  typical  endoge- 
nous stem  has  no  clear  distinction  of  pith, 
bark,  and  wood,  concentrically  arranged, 
no  silver  grain,  no  annual  layers,  no  bark 
that  peels  off  clean  from  the  wood. 

519.  Exogenous  stems,  those  of  plants 

coming  from  dicotyledonous  and  also  polycotyledonous 
embryos,  have  a  structure  which  is  familiar  in  the  wood  of 
our  ordinary  trees  and  shrubs.  It  is  the  same  in  an  herba- 


t  ran  averse 

and  longitu- 
dinal section. 
The  dots  on 
the  cross  sec- 
tion repre- 
sent cut  ends 
of  the  woody 
bundles. 


224      MINUTE  ANATOMY  OF  FLOWERING  PLANTS 


ceous  shoot  as  in  a  Maple  stem  of  the  first  year's  growth 
(Fig.  376),  except  that  the  woody  layer  is  commonly  thin- 
ner, or  perhaps  reduced  to  a  circle  of  bundles.  The  wood 


377 


378 


376.  Diagram  of  a  cross  section  of  a  very  young  exogenous  stein,  showing  six 
fibro-vascular  bundles.  377.  Same  later,  with  bundles  increased  to 
twelve.  378.  Still  later,  the  wood  of  the  bundles  in  the  form  of  wedges 
filling  the  space,  separated  only  by  thin  lines,  or  medullary  rays,  run- 
ning from  pith  to  bark. 

all  forms  in  a  cylinder  —  in  cross  section  a  ring  —  around 

a  central  cellular  part,  dividing  the  cellular  core  within,. 

the  pith,  from  a  cellular  bark  without.  As  the  wood 
bundles  increase  in  number  and  in  size, 
they  press  upon  each  other  and  become 
wedge-shaped  in  the  cross  section;  and 
they  continue  to  grow  from  the  outside, 
next  the  bark,  so  that  they  become  very 
thin  wedges.  Between  the  wedges  are 
still  thinner  plates  (in  cross  section  lines) 
of  much  compressed  cellular  tissue,  called 
medullary  rays,  which  connect  the  pith 
with  the  bark.  The  plan  of  a  one-year- 
old  woody  stem  of  this  kind  is  exhibited 
in  the  diagrams. 

520.  When  such  a  stem  grows  on  from 

379.  Cross  section  of  year  to  year,  it  adds  annually  a  layer  of 

wood  :     s,    s,    J         ,       \   .,      ,,  ,.  ,    " 

spring  wood;  wood  outside  the  preceding  one,  between 

/,  fail  wood.'  that  and  the  bark  (Fig.  379).     This  is 

exogenous  growth,  or  outside  growing,  as  the  name  denotes. 

521.    Some  new  bark  is  formed  every  year,  as  well  as 

new  wood,  the  former  inside,  as  the  latter  is  outside  of 

that  of  the  year  preceding. 


MINUTE  ANATOMY  OF  FLOWERING  PLANTS      225 


522.  The  Bark  of  a  year-old  stem  consists  of  three  parts, 
more  or  less  distinct,  namely,  —  beginning  next  the 
wood,  — 

1.  The  liber,  or  fibrous  bark,  the  inner  bark  (Fig.  380, 
1).     This  contains  the  bast  fibers,  the  walls  of  which  are 
commonly  lignified,  and  other  ele- 
ments, as  already  briefly  described. 

In  woody  stems,  whenever  a   new    3 
layer  of  wood  is  formed,  some  new 
liber  or  inner  bark  is  also  formed 
outside  of  it. 

2.  The  green  or  middle  Bark  (Fig. 
380,  2).      This  consists    mainly  of 
rounded  parenchyma  cells,  contain- 
ing chlorophyll   granules   like   the 
cells  of  the  leaf.     The  green  bark 
of  twigs  functions  as  assimilating 
tissue  in  the  same  way  as  the  leaf 
parenchyma. 

3.  The  corky  layer  or  outer  bark 
(Fig.  380,  3),  consisting  of  empty, 
angular  cells,  closely  coherent,  the 
walls  of   which    are    suberized,    or 
chemically  altered  in  such  a  man- 
ner as  to  be  impermeable  to  water. 

TJ_  •      ji  •         i  •   i        •  j_i  380.  Cross  section  through 

It  IS   this  Which   gives   to  the  Stems  bark  into  the  wood  of 

or  twigs  of   shrubs   and   trees  the  a  Lilac  twig:  e,  epi- 

aspect  and  the  color  peculiar  to 
each,  —  light  gray  in  the  Ash,  pur- 
ple in  the  Red  Maple,  red  in  several 
Dogwoods,  etc. 

Sometimes  the  corky  layer  grows 
and  forms  new  layers  inside  the  old  for  years,  as  in  the 
Cork  Oak,  which  produces  the  cork  of  commerce,  the 
Sweet  Gum  Tree,  and  the  White  and  the  Paper  Birch. 
This  growth  proceeds  from  a  formative  layer,  called  the 
cork  cambium,  lying  on  the  inner  boundary  of  the  cork. 
The  old  cork,  being  dead  and  therefore  incapable  of 

OUT.  OF  EOT.    —  15 


dermis;  c,  cork;  p, 
collenchyma;  g,  green 
rounded  cells ;  /,  bast 
fibers ;  ca,  cambium  ; 
w,  wood;  1,  2,  3,  in- 
ner, middle,  and  outer- 
bark. 


226      MINUTE  ANATOMY  OF  FLOWERING  PLANTS 

growth,  is  stretched,  and  finally  rent  by  the  continual 
enlargement  of  the  wood  within;  it  is  weathered  and 
worn,  and  thrown  off  in  fragments,  in  some  trees  rapidly, 
in  others  more  slowly,  so  that  the  bark  of  old  trunks 
may  acquire  great  thickness.  Similarly  in  Honeysuckles 
and  Grapevines,  the  layers  of  the  inner  bark  or  liber 
loosen  and  die,  and  come  off  in  strips  when  only  a  year 
or  two  old. 

523.  The  epidermis,  consisting  of  a  single  layer  of  close- 
fitting,  tabular  cells,  with  outer  walls  much  thickened  and 
coated  with  a  layer  of  matter  impermeable  by  water,  per- 
sists only  for  the  first  year  or  two.     It  is  found,  therefore, 
in  the  case  of  stems,  only  on  herbaceous  plants,  and  on  the 
twigs  and  young  parts  of  perennials,  as  a  rule. 

ANATOMY  OF  LEAVES 

524.  In  the  framework  of  leaves  —  ribs,  veins,  and  vein- 
lets  —  all  the  usual  elements  of  vascular  tissue  are  repre- 
sented.    The   midrib,    for    instance,   possesses   a   typical 
fibre-vascular  bundle,  with   phloem  and  xylem  portions, 
derived  from  the  branching  of  the  fibro-vascular  system 
of  the  stem.     In  the  veinlets,  however,  the  conducting 
elements  become  reduced  to  simple  series  of  hollow  cells 
and  fibers.     The  woody  framework  serves  not  only  to 
strengthen  the  leaves,  but  also  to  bring  in  sap  and  to 
distribute  it  throughout  every  part. 

525.  The  living  cells  of  the  leaf,  making  up  the  green 
pulp,  are  of  various  forms,  usually  loosely  arranged,  so  as 
to  give  copious  intercellular  spaces  or  air  passages  commu- 
nicating throughout  the  whole  interior  (Figs.  381,  382). 
The  green  color  is  given  by  the  chlorophyll  grains,  seen 
through  the  transparent  walls  of  the  cells  and  through  the 
translucent  epidermis  of  the  leaf. 

In  ordinary  leaves,  having  an  upper  and  under  surface, 
the  green  cells  form  two  distinct  strata,  of  different  arrange- 
ment. Those  of  the  upper  stratum  are  oblong  or  cylindri- 
cal, and  stand  endwise  to  the  surface  of  the  leaf,  usually 


MINUTE  ANATOMY  OF  FLOWERING  PLANTS      22? 

rather  close  together,  leaving  scanty  vacant  spaces ;  those 
of  the  lower  are  commonly  irregular  in  shape,  most  of  them 
with  their  long  diameter  parallel  to  the  face  of  the  leaf, 
and  are  very  loosely  arranged,  leaving  many  and  wide  air 
chambers.  The  green  color  of  the  lower  is  therefore 


381.  Magnified  section  of  a  leaf  of  White  Lily,  to  exhibit  the  cellular  struc- 
ture, both  of  upper  and  lower  stratum,  the  air  passages  of  the  lower, 
and  the  epidermis  in  section;  also  a  little  of  the  lower  face,  with 
some  of  its  stomates. 


diluted,  and  paler  than  that  of  the  upper  face  of  the  leaf. 
The  upper  part  of  the  leaf  is  so  constructed  as  to  bear  the 
direct  action  of  the  sunshine;  the  lower  so  as  to  afford 
freer  circulation  of  air,  and  to  facilitate  the  escape  of  mois- 
ture. It  communicates  more  freely  than  the  upper  with 
the  external  air  by  means  of  pores  in  the  epidermis. 

526.  The  upper  cylindrical  cells  are  known  as  the  pali- 
sade cells.     The  lower,  irregular,  or  sometimes   slightly, 
branching  cells  make  up  the  spongy  parenchyma,  so  called. 

527.  The  epidermis  is  usually  composed  of  a  single  layer 
of  more  or  less  flattened  cells,  devoid  of  chlorophyll,  and 
mostly  of  irregular  outline  (Figs.  382,  383). 

The  walls  of  the  epidermis  are  commonly  thickened 
externally  by  the  addition  of  a  layer  of  a  waterproof  sub- 
stance. This  layer  is  easily  distinguished  in  the  cross 
section  from  the  original  exterior  walls  of  the  cells.  It 
is  termed  the  cuticle.  The  several  walls  of  each  epider- 
mal cell  are  impregnated  with  the  same  waxy  or  fatty 


228      MINUTE  ANATOMY  OF  FLOWERING  PLANTS 


matters  which   give   the   cuticle  its  resistance  to  water. 

These  walls  are  said  to  be  cutinized. 

528.    The  pores  of  the  epidermis  are  called  stomates  or 

stomata  (i.e.  mouths).     Each  stomate  (^stoma)  is  guarded, 

so  to  speak,  by  two  cells  of 
peculiar  conformation,  called 
guard  cells  (Figs.  382,  383,  g). 


g       8 

382.  Section  of  a  leaf :  e,  epidermis;  383.  Surface  view  of  e  idermis  of 

c,assimilatingcellscontain-  the  leaf .  e>  ordinary  epider. 

ing   chlorophyll    granules;  mal  cell;   gy  guard  cell.  - 

p,  intercellular    passages;  TSCHIRCH. 
g,  g,  guard  cells  of  stomate. 

The  guard  cells,  unlike  the  rest  of  the  epidermis,  contain 
chlorophyll.  They  are  so  constructed  that  as  the  quantity 
of  water  they  contain  varies  the  slit 
between  them  is  either  opened  wider, 
or  narrowed,  —  or,  it  may  be,  quite 
closed.  The  guard  cells  are  closed 
together  when  flaccid  on  account  of 
the  wilting  of  the  leaf. 

Stomates  are  found  on  most  of  the 
green  surfaces  of  the  plant,  but  most 
abundantly  on  the  leaf.  Here  they 
are  generally  more  numerous  on  the 
under  side. 

529.  Trichomes  are  outgrowths  of 
the  epidermis,  consisting  in  the  sim- 
plest cases  of  single  cells,  but  in  many 

384.  Trichomes   (h,  h)    of    J 

the  leaf.  — SACHS,     cases  of  several  cells  in  a  more  or  less 


BEIEF  OUTLINE  OF   VEGETABLE  PHYSIOLOGY     229 

complicated  arrangement.  Several  different  kinds  may 
spring  even  from  the  same  leaf  (Fig.  384).  Stinging 
hairs  (Fig.  360)  and  hairs  with  bitter  secretions  are  an 
important  means  of  defense  to  many  plants. 

530.  The  anatomy  of  the  root  resembles,  in  a  general 
way,  that  of  the  stem.     There  is  a  central  conducting 
and  strengthening  strand  of  wood.     In  the  older  roots  of 
perennial   exogenous   plants  this  becomes  a  cylinder  of 
wood  surrounded  by  a  cambium  zone,  from  which  wood 
is  formed  annually  just  as  in  the  stem.     The  cortex  of 
the  older  parts  of  many  roots  is  bounded  externally  by 
several  layers  of  cork  cells,   preventing  the  passage  of 
water  into  or  out  of  the  root.     Formation  of  new  tissue 
for  growth  in  length  takes  place  at  the  growing  point 
(Fig.    28,  g)    under   the   root   cap.      New   lateral   roots 
originate  from  cells  lying  near  the  wood,  and  push  their 
way  through  the  cortex  to  the  surface.     They  arise  in 
longitudinal  rows. 

XVIII.    A  BRIEF  OUTLINE  OP  VEGETABLE 
PHYSIOLOGY1 

531.  Vegetable  physiology  deals  with  the  processes  by  which  the 
life  of  plants  is  carried  on.      Such  processes  are  the  absorption  of 
materials ;  the  transfer  of  raw  and  elaborated  food  matters  from  one 
part  of  the  plant  body  to  another ;  the  conversion  of  inorganic  matters 
into  organic  substance ;  the  storage  of  elaborated  products ;    respira- 
tion and  the  consumption  of  food  for  the  production'  of  vital  energy ; 
growth ;  and  movement. 

532.  Constituents  of  the  plant  body.  —  The  chief  constituent,  as 
concerns  quantity,  is  water,  since  even  in  woody  parts  the  solid  por- 
tions amount  at  most  only  to  fifty  per  cent  of  the  total  weight,  and 
in  herbaceous  parts  to  but  twenty  or  thirty  per  cent. 

533.  We  may  distinguish  three  ways  in  which  water  is  useful  to 
the  plant:  (1)  it  furnishes  part  of  the  raw  material  out  of  which 

1  A  number  of  experiments  in  vegetable  physiology  and  some  informa- 
tion as  to  the  general  function  of  plants  have  already  been  given  in  this 
book.  The  present  chapter  is  added  for  the  purpose  of  gathering  together 
in  coherent  form  the  results  of  these  previous  studies.  As  discussions  of 
the  most  important  matters  will  be  held  in  the  class  room,  following 
experimentation  in  the  laboratory,  the  chapter  may  be  used  for  reference 
rather  than  for  ordinary  assignment  in  lessons. 


230      BRIEF  OUTLINE  OF   VEGETABLE  PHYSIOLOGY 

substances  like  starch  and  cellulose  are  formed ;  (2)  it  is  the  solvent 
in  which  all  the  vital  chemical  changes,  like  assimilation,  are  carried 
on ;  (3)  its  presence  is  an  important  factor  in  preserving  the  rigidity 
of  the  plant  body.  The  first  of  these  offices  has  been  touched  upon 
in  the  brief  statement  of  assimilation  made  in  the  chapter  on  the 
Leaf.  The  second  need  not  be  further  dwelt  upon.  The  third  mav 
now  be  more  fully  considered,  since  it  concerns  a  first  essential  to  the 
existence  of  the  plant,  namely  :  — 

534.  The  stability  of  the  plant  body.  —  By  stability  is  meant  the 
power  of  the  plant  to  keep  its  form,  —  the  power,  if  it  is  an  erect 
plant,  of  keeping  itself  erect  and  outspread  in  proper  position  in  all 
its  parts.     It  is  a  matter  of  common  observation  that  plants  suffering 
from  drought  wilt  and  droop,  sometimes  even  fall  flat  to  the  ground. 
Wilted  plants  have  partly  or  wholly  lost  their  stability. 

535.  Stability  is  secured  in  part  by  the  properties  of  the  tissues 
themselves ;  the  thick-walled,  strengthening  fibers  are  so  disposed  in 
the  stem  as  to  secure  the  greatest  rigidity.     But  in  herbaceous  and 
succulent  organs,  firmness  depends  oftentimes  as  much,  or  more,  upon 
the  condition  of  the  living  cells  in  regard  to  their  supply  of  water. 
When  one  of  these  cells  has  a  full  supply  of  water,  the  expansive  sub- 
stances held  in  solution  by  the  cell  sap  (for  example,  sugar  and  acids) 
are  enabled  to  distend  the  cell  to  its  full  limits.1     The  cell  is  then  said 
to  be  turgid. 

In  such  a  condition  it  resists  the  distorting  stresses  brought  upon  it 
by  the  pulls  of  neighboring  cells.  And  when  all  the  cells  of  a  tissue 
are  fully  turgid,  they  resist,  collectively,  all  distorting  stresses.  That 
member  of  the  plant  body  which  is  well  watered,  therefore,  retains  its 
form  and  proper  attitude. 

536.  The  turgidity  of  cellular  tissues  gives  rise  to  tensions  between 
different  masses  of  tissue  lying  side  by  side  in  the  plant  body.    A  good 
illustration  of  these  tissue  tensions  is  furnished  by  the  succulent  stalk 
of  a  Rhubarb  leaf.     Let  a  portion  of  the  fresh  stalk  be  cut  squarely 

1  Dissolved  substances  have  an  expansive  force,  comparable  in  a  gen- 
eral way  to  the  expansive  force  of  gases.  Sugar  dissolved  in  cell  sap  presses 
against  the  protoplasm  that  holds  it  in,  just  as  hydrogen  presses  against 
the  walls  of  a  balloon.  The  cell,  in  such  a  case,  has  a  constant  tendency 
to  expand.  If  water  is  at  hand  that  can  come  in  to  occupy  the  additional 
space  to  be  made  by  expansion,  then  the  cell  expands  until  the  outward 
push  of  the  solutions  equals  the  resistance  of  the  cell  wall  to  being  stretched. 
The  entrance  of  water,  therefore,  is  the  result  of  the  expansive  tendency  of 
the  cell  sap  solutions.  Water  does  not  cause  the  swelling,  only  allows  it. 
Absorption  of  water  by  such  action  is  called  osmotic  absorption. 

For  a  clear  statement  of  the  theory  of  osmotic  pressure,  see  Ostwald's 
"Solutions,"  Eng.  4,rans.  The  theory,  however,  has  received  important 
additions  since  the  work  named  was  published. 


BRIEF  OUTLINE  OF  VEGETABLE  PHYSIOLOGY     231 

off  at  the  ends,  and  its  length  be  exactly  measured.  Let  the  stringy 
external  sheath  then  be  stripped  off,  and  at  once  let  both  the  central 
cellular  column  and  one  or  two  of  the  external  strips  be  measured.  It 
will  be  found  that  the  pith  has  considerably  lengthened,  while  the 
fibrous  strips  are  somewhat  shorter  than  the  piece  of  leaf  stalk  origi- 
nally measured.  Before  separation,  then,  the  pith  must  have  been 
compressed,  the  external  tissues  stretched.  Tissue  tensions  add  rigid- 
ity to  stems,  petioles,  etc.  Variations  in  tissue  tensions  give  rise  to 
curvatures  of  organs,  such  as  the  bending  of  the  stem  toward  the 
light. 

537.  Solid  components  of  the  plant  body.  —  By  solid  components 
is  meant  here  all  the  matter  left  when  water  has  been  entirely  driven 
off  by  heat  at  somewhat   above  the  boiling  temperature  of  water. 
This  includes  cell  walls,  dried  living  substance  (protoplasm),  starch, 
sugar,  and  other  formed  matters  in  the  cells,  and  small  amounts  of 
mineral  matters  ordinarily  held  in  solution  in  the  juices  of  the  plant 
or  deposited  in  the  tissues  in  crystalline  form. 

538.  Amongst  these,  the  organic  constituents  are  composed  almost 
solely  of  the  four  chemical  elements  —  carbon,  hydrogen,  oxygen,  and 
nitrogen.     Organic  matters  belonging  to  the  class  carbohydrates  —  as 
sugar,  starch,  cellulose  —  and  fats,  include  in  their  composition  only 
the  first  three  of  these  elements;   they  lack  nitrogen.     Nitrogenous 
organic  compounds  —  as  those  that  make  up  protoplasm — contain  all 
the  four  elements  named,  and  in  addition,  usually  a  small  amount  of 
sulphur  and  phosphorus. 

539.  The  nature  of  the  mineral  matters  held  in  the  plant  is  found 
when  the  dried  plant  has  been  burned  and  the  ash  has  been  chemically 
analyzed.     In  burning,  carbon  and  hydrogen  are  united  with  oxygen 
from  the  atmosphere  and  pass  away  in  a  gaseous  form.     Organic  com- 
ponents of  the  plant  body  are  therefore  broken  up.     The  ash  that  is  left 
is  entirely  inorganic.     In   such  ash,  from  various  plants,  has  been 
found  a  large  part  of  all  the  known  chemical  elements,  including  even 
the  rarer  metals.     Most  of  these  elements  occur  accidentally,  being 
absorbed  with  soil  water.     But  certain  of  the  chemical  elements  are 
absolutely  necessary  to  the  healthy  growth  of  every  green  plant.    These 
are  six  in  number;   viz.,  sulphur,  phosphorus,  potassium,  calcium, 
magnesium,  iron. 

540.  Source  of  the   elements.  —  Thus  there   are,   including  the 
four  elements  before  named  as  chiefly  making  up  organic  substance, 
in  all  ten  elements  which  must  be  furnished  the  growing  plant.     Each 
of  these  is  received  by  the  plant  in  a  combined  form.     Carbon  comes 
from  the  atmosphere,  combined  with  oxygen,  as  carbonic  acid  gas. 
All  the  other  needful  substances  come  from  the  soil.     Hydrogen  and 
oxygen  come  together,  as  water.     Nitrogen  is  brought  in  under  the 
form  of  a  soluble  nitrate,  or  one  of  the  ammonia  salts,  in  the  absorbed 


232      BRIEF  OUTLINE  OF  VEGETABLE  PHYSIOLOGY 

soil  water.     Sulphur,  phosphorus,  potassium,  etc.,  are  obtained  in  the 
form  of  salts  from  the  soil. 

541.  As  regards  the   number  of  elements  supplied,  the  root  is 
therefore  the  chief  organ  of  absorption  ;  the  leaf  absorbs  only  carbonic 
acid   gas. l     Absorption    at  the   root   may  be  considered  under  two 
heads  :  absorption  of  water,  and  absorption  of  nutrient  salts. 

542.  Absorption  of  water.  —  The  manner  in  which  the  root  sends 
out  root  hairs,  which  become  applied  to  the  soil  particles   for  the 
purpose  of  absorption,  has  been  described  in  an  earlier  chapter.     What 
force   acts  to  draw  water  into  the  root  hairs   is  not  known   with 
certainty.     It  is  believed  by  most  physiologists  to  be  the  osmotic  force 
of  the  root  hair  cells  (see  page  230,  footnote). 

543.  Aside  from  the  scarcity  or  abundance  of  water  in  the  soil, 
the  chief  external  circumstance  affecting  the  rate  of  absorption  is  that 
of   temperature.     Warmth  increases  absorptive  activity,   while  cold 
decreases,  or  even  prohibits  it.     Sachs  found  that  at  a  temperature  of 
from  38°  to  41°  F.  absorption  of   water  ceased,  in  spite  of  the  fact 
that  the  soil  was  saturated. 

544.  Absorption  of  nutrient  salts.  —  The  salts  needed  for  perfect 
nutrition  may  be  swept  into  the  plant  in  the  absorption  current.     In 
case  the  salts  are  bound  by  adhesive  force  to  the  soil  particles,  they 
must  first  be  loosened  by  the  action  of  acids  excreted  by  the  root 
hairs.     When  they  exist  in  free  solution  in  the  soil  water,  or  have 
been  brought  into  this  condition  by  the  secretions,  they  may  pass  into 
the  root  hair  quite   independently  of  any  current,   by  the  process 
known   as   diffusion.     The   dissolved  particles   of    the  salt    wander 
throughout  the  body  of  water  in  which  they  find  themselves,  through 
the  root-hair  walls,  and  so  on  through  the  tissues  of  the  plant  body, 
unless  they  meet  membranes  possessing  pores  too  minute  to  allow 
of  their  entrance.     Those  salts  that  are  most  used  by  the  active  cells 
and  are  therefore  scarcest  in  the  general  sap  of  the  plant,  diffuse 
from  the  soil  into  the  plant  more  rapidly  than  those  that  are  little 
used  and  that  therefore  tend  to  become    concentrated  in  the   sap. 
Each  kind  of  plant,  according  to  its  nature,  by  internally  appropri- 
ating more  or  less  of   this   or  that  salt,  thus   controls  the  absorp- 
tion of  the  different  soil  salts  at  the  root.      Some  kinds  of  plants 
tend  to  exhaust  one  constituent  of  the  soil,  some  kinds  another  con- 
stituent.    Plants  are   therefore   said  to   show   selective  absorption   of 
nutrient  salts. 

545.  The  transfer  of  water  through  the  root  and  stem  to  the  leaf 
is  accomplished  by  a  number  of  forces.     In  the  case  of  deciduous  trees 

1  Like  all  other  parts  of  the  plant,  the  leaf  absorbs  oxygen  for  respira- 
tion. But  we  are  here  considering  the  raw  materials  from  which  food  is 
formed. 


BRIEF  OUTLINE  OF  VEGETABLE  PHYSIOLOGY     233 

in  spring,  before  the  leaves  appear,  the  sap  may  press  up  into  the 
trunk  and  on  toward  the  buds  with  considerable  force.  Or  again,  if 
in  an  herbaceous  plant  evaporation  of  water  from  the  leaves  is  checked, 
the  sap  may  press  into  the  leaves  so  strongly  that  drops  exude  from 
the  leaf  tips  or  from  the  marginal  teeth  —  usually  in  those  cases  from 
definite  water  pores.  The  drops  seen  at  the  tips  of  grass  blades  after 
a  warm,  damp  night,  are  of  this  sort.  In  all  these  cases  the  rise  of 
water  in  the  plant  is  due  to  what  is  termed  root  pressure. 

546.  The  phenomenon  of  root  pressure  may  be  observed  when  the 
stem  of  a  plant,  such  as  the  Sunflower,  is  cut  off  near  the  ground. 
After  a  time  water  (sap)  begins  to  run  from  the  cut.     If  now  an  effort 
is  made  to  stop  the  outflow,  a  considerable  force  must  be  used  before 
the  pressure  of  the  sap  —  the  so-called  root  pressure  —  is  neutralized. 
Hales,  the  earliest  of  exact  physiological  botanists,  who,  about  1731, 
made  some  measurements  of  the  root  pressure  of  the  Grapevine,  found 
it  to  be  equal  to  the  downward  pressure  of  a  column  of  water  forty- 
three  feet  high.     A  pressure  of  sap,  equal  to  the  pressure  of  eighty-five 
feet  of  water,  has  been  observed  in  a  Birch.     Root  pressure  falls  to 
nothing,  however,  when  the  loss  of  water  at  the  leaf  is  going  on  with 
any  rapidity.     Root  pressure,  therefore,  cannot  continuously  supply 
the  leaves  with  the  water  they  need. 

547.  The  ascent  of  water  in  the  stem  has  been  the  subject  of  many 
investigations  and  much  discussion.     The  path  followed  by  the  cur- 
rent is  the  cavities  of  the  ducts  and  fibers  of  the  wood.     The  force 
working  to  raise  the  water  in  these  cavities  is  not,  to  any  considerable 
extent,  capillarity,   as  was  once  supposed.      The  ultimate  cause  is 
doubtless  the  evaporation  of  water  from  the    leaves ;   but  how  this 
works  to  raise  water  through  the  stem  is  still  a  disputed  question. 

548.  Evaporation  of  water  from  the  shoot;   transpiration.  —  Land 
plants  are  perpetually  giving  off  water  vapor  from  their  parts  above 
ground,  in  greater  or  smaller  quantities  according  to  external  circum- 
stances or  internal  peculiarities.     Even  in  winter  the  twigs  of  trees 
transpire  a  little.     In  desert  plants  transpiration  is  reduced  to  almost 
nothing  in  the  dry  season. 

549.  Leaves  are  the  especial  organs  of  transpiration  in  ordinary 
cases.     Though  their  surfaces  are  covered  with  an  epidermis  that  pre- 
vents too  great  loss  of  water,  the  pores  or  stomates  allow  a  regulated 
escape  of  vapor  which  is  of  great  importance  to  the  plant.     The  inter- 
cellular passages  of  the  spongy  tissue  furnish  communication  between 
the  leaf  cells,  saturated  with  water,  and  the  atmosphere  without.     As 
long  as  the  stomates  remain  open,  therefore,  vapor  given  off  by  the 
moist  walls  of  the  cells  escapes  from  the  leaf.     When  the  stomates 
close  from  any  cause,  the  exit  of  vapor  is  checked.     Even  then,  how- 
ever, some  evaporation   takes  place  through  the  cuticle,  which  is 
imperfectly  waterproof  in  most  plants. 


234      BEIEF  OUTLINE   OF   VEGETABLE  PHYSIOLOGY 

550.  The  amount  of  water  lost  by  transpiration  varies  very  greatly 
with  the  character  of  the  plant  and  the  conditions  under  which  it  is 
placed.     The  early  experimenter  Hales,  by  weighing,  determined  the 
loss  from  a  potted  Sunflower  plant,  three  feet  and  a  half  high,  to  be 
on  the  average  one  pound  four  ounces  every  twelve  hours.     From  this 
some  idea  may  be  formed  of  the  very  large  weight  of  water  transpired 
by  a  full-grown  tree  on  a  warm  day.     It  has  been  estimated  that  the 
amount  of  aqueous  vapor  given  off  by  an  acre  of  Beech  forest  between 
June  1  and  December  1  is  between  1000  and  1500  tons. 

551.  The  object  of  the  transpiratory  activity  is  the  acquirement  of 
nutrient  salts  from  the  soil  and  their  transportation  to  the  leaves, 
where  they  are  left  by  the  evaporation  of  the  water. 

552.  The  rate  of  transpiration  is  regulated  in  part  by  the  action  of 
the  stomates.     When  the  guard  cells  of  a  stomate  are  turgid  the  slit 
between  them  stands  wide  open.     If  the  guard  cells  become  flaccid, 
either  through  undue  wilting  of  the  leaf  or  from  any  other  cause,  the 
stomatal  opening  becomes  narrowed  or  closed.     The  guard  cells  are 
sensitive  to  the  influence  of  light;  in  bright  sunshine  the  stomates 
stand  wider  open  than  in  diffused  light,  and  they  close  on  dark,  stormy 
days  even  in  summer.     Artificial  darkness  closes  them  —  more  quickly 
in  the  afternoon  than  in  the  morning.     At  night  the  majority  of  plants 
close  their  stomates,  but  not  so  as  to  prohibit  all  transpiration.     The 
stomatal  cells  are  sensitive  also  to  dryness.     A  draught  of  dry  air 
causes  them  to   close,   eveir  though   the   leaves  show  no   signs   of 
wilting. 

553.  Aside  from  stomatic  regulation,  the  rate  of  transpiration  for 
any  given  plant  depends  largely  upon  the  external  circumstances  of 
heat,  light,  dampness,  or  dryness  of  the  atmosphere  and  supply  of 
water  at  the  root.      Heat  furnishes  the  energy  for  all  evaporation ; 
consequently,  rise  of  temperature  in  the  leaf  accelerates  transpiration. 
Light  also  has  a  stimulating  effect.     Dampness  of  the  air  around  the 
leaf,  on  the  contrary,  retards  transpiration,  just  as  it  checks  ordinary 
evaporation.     And  of  course  dryness  of  the  soil  acts  finally  to  reduce 
the  amount  of  transpiration. 

554.  Assimilation  of  carbon.  —  Carbon  is  the  most  important  of  the 
elements  going  to  make  up  the  solid  parts  of  the  plant  body.      How 
great  a  proportion  of  the  framework  it  forms  is  seen  when  wood  is 
subjected  to  great  heat  in  the  absence  of  air.     Everything  volatile 
is   then   driven   off;    but  the  form   remains,   even  the    microscopic 
details  of  structure  being  preserved  by  the  carbon  of  the  charcoal. 
Carbon  constitutes,  by  weight,  about  one-half  of  the  dry  substance  of 
ordinary  plants. 

555.  Carbon  dioxide,  the  source  of  this  important  element,  enters 
the  leaf  through  the  stomates,  passes  along  the  intercellular  spaces 
of  the  spongy  tissue,  becomes  dissolved  in  the  water  that  saturates 


BRIEF  OUTLINE  OF  VEGETABLE  PHYSIOLOGY     235 

the  walls  of  the  cells,  and  then  diffuses  throughout  the  green  tissue. 
Its  goal  is  the  chlorophyll  granules.  1  Here,  in  sunlight,  its  particles 
are  torn  apart,  and  the  carbon  atoms  are  combined  with  the  atoms  of 
hydrogen  and  oxygen  derived  from  the  decomposition  of  water,  to 
form  a  carbohydrate.  This  carbohydrate,  if  not  starch,  is  shortly 
turned  to  starch  as  a  rule,  appearing  as  minute  granules  in  the  chloro- 
plastids  sometimes  within  five  minutes  after  exposure  of  the  plant  to 
light.  These  granules  increase  in  size  while  assimilation  continues; 
but  when  assimilation  ceases,  as  at  night,  the  starch  begins  to  be 
dissolved,  and  is  finally  conveyed  away  in  the  form  of  a  soluble 
carbohydrate.  Assimilation  of  carbon  by  aid  of  light  is  termed  photo- 
synthetic  assimilation. 

556.  The  conditions  that  must  be  fulfilled  before  assimilation  will 
take  place  are  these :  Carbonic  acid  gas  must  be  present  in  the  atmos- 
phere, there  must  be  light  and  a  certain   amount  of  heat,  and  the 
chloroplastids  must  contain  chlorophyll. 

557.  The  atmosphere  normally  contains  about  .04  of  one  per  cent 
of  carbonic  acid  gas,  by  weight.     Increasing  this  proportion  hastens 
the   rate  of  assimilation    slightly;   but  if   the   gas  is  increased  two 
hundred  fold,  the  formation  of  starch  becomes  only  four  or  five  times 
greater.     Ordinary  variations  in  the  amount  of  carbon  dioxide  would, 
therefore,  not  perceptibly  aid  assimilation. 

558.  Light  furnishes  the  energy  of  assimilation.     Of  the  different 
components  of  white  light,  the  red,  orange,  and  yellow  rays  are  the 
most  effective. 

559.  Liberation  of  oxygen.  —  In   the  act   of   assimilation,  when 
carbon  is  taken  into  the  material  of   the   plant,  the  oxygen  of  the 
carbon  dioxide  is  given  off.     In  the  case  of  water  plants  this  may  be 
seen.     Let  a  cut  branch  of  such  a  plant  be  exposed  to  light  under 
water.     Bubbles  of  oxygen  will  be  seen  escaping  from  the  cut  end. 
The  rapidity  with  which  these  bubbles  are  given  off  may  be  taken  as 
a  convenient  measure  of  the  activity  of  assimilation  in  the  given  plant 
under  the  given  circumstances.     If,  for  example,  the  plant  is  exposed 
to  one  sort  or  one  intensity  of  light  for  a  period,  and  the  number  of 
bubbles  rising  from  it  per  minute  is  found,  the  conditions  as  to  light 
may  then  be  varied,  and  the  number  of   bubbles  per  minute  ascer- 
tained anew ;  compared  with  the  former  result,  the  later  count  will 
show  whether  the  assimilative  activity  of  the  plant  is  greater,  or  less, 
under  the  new  conditions.  2 

560.  The  action  by  which  substances  like  starch  and  protein  gran- 
ules, insoluble  in  the  sap,  are  converted  into  soluble  compounds  is 
digestion.     In  digestion,  starch  is  changed  to  sugar.      In  the  latter 

1  See  Fig.  382,  Chap.  XVII. 

2  See  Goodale,  "  Physiological  Botany,"  p.  305,  for  more  explicit  direc- 
tions.    The  experiments  are  most  interesting. 


236      BRIEF  OUTLINE  OF  VEGETABLE  PHYSIOLOGY 

form  the  newly  made  plant  food  in  the  cells  of  the  leaf  can  pass  out 
through  the  petiole  to  the  stem,  and  travel  to  points  of  active  growth, 
or  to  storage  cells.  Digestion  is  accomplished  by  means  of  the  so- 
called  ferments,  or  enzymes,  of  which  diastase  is  a  common  example. 
The  enzymes  are  not  consumed  in  the  process;  their  mere  presence 
seems  to  be  enough  to  induce  digestion.  Diastase  is  extracted  from 
germinating  seeds  (e.g.  barley).  If  a  solution  is  applied  to  a  bit  of 
starch  on  a  glass  slide  under  the  microscope,  the  disintegration  of  the 
starch  granules  may  be  observed.1 

561.  The  formation  of  albuminous   substances. —  Assimilation    is 
only  the  first  step  toward  the  formation  of  living  substance,  or  proto- 
plasm.    The  albuminous  substances  which  compose  protoplasm  differ 
from  the  carbohydrates  produced  by  assimilation,  in  containing  a  con- 
siderable proportion  of  nitrogen  often  with  some  sulphur  and  phos- 
phorus.    It  is  in  the  formation  of  these  nitrogenous,  or  albuminous, 
matters  that  the  nutrient  mineral  salts  are  put  to  use.     Where  this 
final  step  in  the  production  of  proteid  matter  is  taken  is  not  definitely 
known.     It  may  be  that  it  is  in  the  green  tissue  of  the  leaf,  or  it  may 
be  at  all  growing  points. 

562.  The  transfer  of  organic  substance,  whether  of  carbohydrates 
or  of  nitrogenous  compounds,  is  largely  accomplished  by  the  diffusion 
of  solutions  of  these  substances.     Albuminous  matters  not  diffusible, 
as  well  as  solutions,  are  carried  by  the  so-called  sieve  tubes  in  the  bark, 
when  the  transfer  takes  place  in  a  dicotyledonous  stern.2     This  is  the 
route  by  which  nourishment  designed  for  the  root  system  is  brought 
from  the  leaves.     If  a  ring  of  bark  is  removed  from  the  trunk  of  a 
tree,  the  bark  above  the  cut  grows  and  swells  out,  because  of  the 
arrest  and  accumulation  of  nourishment  in  transit  toward  the  root. 

563.  Storage.  —  Such  a  part  of  the  elaborated  food  as  is  not  at  once 
needed  for  growth  passes  into  the  store  of  reserve  material. 

564.  Living  cells  perform  the  office  of  storage.     In  stems  and  roots 
these  cells  would  be  those  of  the  bark,  the  medullary  rays,  and  the 
living  pith.     In  tubers  and  other  special  organs  of  storage,  the  storage 
cells  are  particularly  numerous  and  often  of  large  size. 

565.  Carbohydrates  are  stored   most  commonly  in   the  form  of 
starch,  but  also  in  the  form  of  sugar.     Reserve  cellulose  is  another 
storage  condition  of  the  carbohydrates ;  in  this  case,  the  walls  of  the 
storage  cells  become  greatly  thickened  by  the  depositions.     Food  may 
be  stored  in  the  form  of  oil  and  fat ;    also  in  protein  granules  and 
crystals. 

566.  Respiration.  —  All  plants,  like  all  animals,  take  in  oxygen. 
As  plants  are  less  active  than  animals,  they  need  less  oxygen ;  and 

1  See  Enzymes,  Strasburger,  p.  203. 

2  In  the  phloem  of  the  fibrovascular  bundles.      For  sieve  tubes  see 
Goodale,  p.  91. 


BRIEF  OUTLINE  OF   VEGETABLE   PHYSIOLOGY     237 

they  have  no  special  organs  of  respiration  comparable  to  the  lungs  of 
animals.  Yet  special  contrivances  exist  which  facilitate  the  passage 
of  oxygen  from  the  atmosphere  to  every  part  of  the  plant.  Inter- 
cellular passages  penetrating  the  tissues  communicate  externally  with 
the  stomates,  and  with  larger  pores  in  the  bark,  called  lenticels.  Len- 
ticels  are  slight  outgrowths  of  the  cork,  in  which  the  cells  lie  loosely 
upon  one  another,  and  over  which  the  epidermis  is  broken  away.  They 
may  be  seen  upon  almost  any  twig.  The  intercellular  spaces  of  water 
plants  are  particularly  large  in  order  to  convey  to  submerged  parts  the 
oxygen  taken  in  through  the  stomates  of  the  leaf ;  or  at  least  in  order 
to  retain  the  oxygen  given  off  by  assimilating  cells.  Oxygen  also 
travels  through  the  tissues  dissolved  in  the  liquids  of  the  cells, 
by  ordinary  diffusion.  In  solution  it  enters  the  ceil  where  it  is 
needed. 

567.  All  living  cells  require  oxygen.     The  effect  of  excluding  oxy- 
gen may  best  be  seen  in  those  cells1  in  which  the  protoplasm  streams, 
—  that  is,  circulates  in  the  cell  more  or  less  rapidly  (Fig.  360).     If 
arrangements   are   made  to  supply   some  other  gas  —  as  carbon  di- 
oxide—  to  the  cell  while  the  circulation  of  the  protoplasm  is  being 
watched  under  the  microscope,  the  movement  is  seen  to  lessen  within 
a  few  seconds  after  oxygen  is  driven  off,  and  shortly  to  stop  altogether. 
If,  after  not  too  long  a  time,  oxygen  is  once  more  admitted,  the  stream- 
ing of  the  protoplasm  begins  again.     But  if  the  suspense  is  too  long, 
the  protoplasm  will  be  found  to  be  dead. 

568.  In  respiration,  the  oxygen  absorbed  by  the  protoplasm  slowly 
oxidizes  it.     There  is,  in  other  words,  a  slow  burning.     Of  course  the 
protoplasm  is  slowly  destroyed,  and  has  to  be  renewed  through  nutri- 
tion.    The  result  of  oxidation,  however,  is  the  generation  of  heat  and 
other  forms  of  energy,  which  enable  the  cells  to  do  their  work.     The 
process  is  essentially  like  that  by  which  energy  is  "  set  free  "  in  the 
burning  of  coal  for  the  driving  of  an  engine.     All  engines,  whether 
organic  or  inorganic,  consume  fuel. 

569.  By  the  oxidizing  process  carbonic  acid  gas  is  formed.     This 
gas  is  easy  to  detect  experimentally,2  and  when  given  off  by  the  plant 
furnishes  the  best  evidence  that  respiration  is  going  on.   Plants  respire 
continuously,  as  long  as  they  live.     But  in  daytime  respiration  is  not 
easy  to  show,  since  the  carbon  dioxide  given  up  by  the  respiring  cells 
is  taken  in  by  the  assimilatory  tissues.     At  night  or  in  darkness,  on 
the  other  hand,  respiration  is  clearly  indicated  by  the  escape  of  the 
telltale  gas. 

1  Such  as  the  new  root  hairs  of  some  aquatics,  the  cells  of  the  leaf  of 
the  fresh-water  Eelgrass,  and  cells  of  the  alga  called  Chara,  and  young 
trichomes  of  many  plants. 

2  See  Experiment  12,  p.  66. 


238      BRIEF  OUTLINE  OF   VEGETABLE  PHYSIOLOGY 


570.  "  The  contrast  between  assimilation  and  respiration  l  is  very 
marked:  one  is  substantially  the  opposite  of  the  other.  The  follow- 
ing tabular  view  displays  the  essential  differences  between  them :  — 


CARBON  ASSIMILATION 

Takes  place  only  in  cells  contain- 
ing chlorophyll. 

Requires  light. 

Carbonic  acid  absorbed,  oxygen 
set  free. 

Carbohydrates  formed. 

[Energy  is  stored.] 

The  plant  gains  in  dry  weight. 


RESPIRATION 
Takes  place  in  all  active  cells. 

Can  proceed  in  darkness. 
Oxygen  absorbed,  carbonic  acid 

set  free. 

Carbohydrates  consumed. 
[Energy  is  brought  into  use.] 
The  plant  loses  dry  weight." 


571.  Resting  periods.  —  The  dormant  condition  of  seeds  and  buds 
has  already  been  described.     In  the  periods  of  suspended  animation 
respiration  is  reduced  to  its  lowest  limits.     Some  seeds  may  be  kept 
for  years  without  loss  of  vitality.    We  must  suppose  that  all  the  while 
the  protoplasm  is  to  a  very  slight  extent  active,  and  that  feeble  respi- 
ration is  going  on. 

572.  Growth.  —  Were  we  to  trace  the  inner  and  outer  changes  that 
lead  to  the  formation  of  a  complete  leaf, — taking  the  leaf  as  an 
example  of  the  organs  in  general,  —  we  should  find   the  following 
course  of  events.     First  a  slight  prominence  is  to  be  seen  close  to  the 
tip  of  the  stem.      This  elevation  is  caused  by  the  rapid  multiplication 
of  the  cells  at  the  point  where  the  new  leaf  is  to  appear.     All  the  cells 
at  this  point  are  capable  of  dividing;   the  tissue  is  said  to  be  embry- 
onic.    Of  course  division  is  accompanied  by  the  increase  in  size  of  the 
cells  produced.     As  the  protuberance  grows,  it  soon  shows  some  signs 
of  external  shaping.     Lobes  appear,  if  the  mature  leaf  is  to  be  lobed 
or  compound.     But  the  whole  mass  of   cells  remains  embryonic  in 
character,  and  the  cells  are  still  relatively  small,  until  the  new  organ 
has  been  formed  and  shaped  into  something  like  a  miniature  of  its 
mature  condition.     Then  another  phase  of  growth  sets  in.     Few  new 
cells,  or  none,  are  made,  but  all  the  cells  begin  to  elongate  and  enlarge. 
As  a  result  the  whole  leaf  expands,  and  it  may  do  so  very  rapidly. 
This  phase  —  the  phase  of  elongation  in  growth  —  is  seen  in  the  swift 
expansion  of  foliage  from  winter  buds  in  spring.     Finally,  as  full  size 
is  being  attained,  a  third  phase  appears.     The  cells  of  the  leaf  indi- 
vidually take  on  their  characteristic  forms,  by  final  changes  in  shape 
and  in  the  nature  of  the  cell  walls. 

573.  Three  phases  are  thus  to  be  made  out  in  the  growth  of  any 
organ :  (1)  the  formative,  or  embryonic  phase ;  (2)  the  phase  of  elonga- 
tion ;  and  (3)  the  phase  of  internal  development.      But  it  is  not  to  be 

1  From  Goodale's  "Physiological  Botany,"  p.  356, 


BRIEF  OUTLINE   OF   VEGETABLE  PHYSIOLOGY     239 

supposed  that  one  phase  ceases  altogether  before  another  begins.    We 
distinguish  the  phases  in  a  general  way. 

574.  Grand  period  of  growth.  —  If  the  elongation  of  a  short  section 
of  a  very  young  growing  part,  as  for  instance  a  section  very  near  the 
tip  of  a  growing  root,  is  marked  off  and  measured  from  time  to  time 
through  several  days,  it  will  be  found  that  at  first  the  rate  of  elon- 
gation in  the   given   section  is   low,  then  gradually  increases  to  a 
grand  maximum,  and  finally  declines  until  growth  disappears.     The 
whole  time  of  growth  of  an  organ,  characterized  by  such  a  general 
rise  and  ultimate  fall  of  the  rate  of  growth,  is  termed  the  grand  period 
of  growth.     Within  this  there  are  minor  variations,  chief  among  which 
are  the  daily  fluctuations. 

575.  Daily  fluctuations.  —  If  the  length  of  a  growing  stem  were  to 
be  measured  at  frequent  intervals  during  the  twenty-four  hours,  it 
would  be  found  that  elongation  does  not  go  on  uniformly.     It  is 
periodic,  being  less  rapid  in  the  daytime  than  at  night.     The  diur- 
nal minimum  is  usually  reached  sometime  in.  the  afternoon;   the 
maximum,  commonly  after  midnight.     This  is  due  to  the  nature  of 
the  plants  themselves,  not  directly  to  the  working  of  external  causes. 
For  if  a  well-nourished  growing  plant  is  kept  for  .several  days  in  the 
dark,  the  periodic  changes  in  growth  rate  still  continue.     All  this  has, 
however,  been  induced  in  plant  nature,  in  the  past,  by  alternation  of 
day  and  night. 

576.  The  chief  external  influences  affecting  growth  are  temperature 
and  light. 

577.  Temperature.  —  Favorable  temperatures  vary  greatly,  accord- 
ing to  the  plant  in  question.    Thus,  in  northern  latitudes  and  on  high 
mountains  certain  species  are  found  growing  vigorously  in  early  spring, 
even  through  a  covering  of  snow,  at  a  temperature  very  slightly  above 
freezing ;  while  most  plants  of  warm  climates  altogether  cease  to  grow 
at  a  temperature  several  degrees  higher.     For  many  common  plants 
the  most  favorable  (optimum)  temperature  is  between  70°  and  85°  F. 

578.  Light  —  In  general,  light  acts  against  growth.     Too  great 
light  may  quite  prevent  growth.     In  nature,  accordingly,  the  rate  of 
elongation  increases  during  the  night,  especially  after  midnight,  and 
decreases  during  most  of  the  day. 

579.  Movement.  —  Transfer  of  substances  in  the  plant,  as  of  water 
or  food  substances,  and  circulation  of  living  protoplasm  in  cells  have 
been  mentioned.     In  the  descriptive  chapters  movements  of  particular 
organs  have  been  noted  in  detail,  as  the  movements  of  roots  of  seed- 
lings, stems,  leaves,  tendrils,  tentacles,  and  floral  organs.     These  activi- 
ties have  now  to  be  briefly  considered  together. 

580.  Most  movements  of  bending  are  due  to  unequal  growth  on 
different   sides  of   the  organs   in   question.      Curvatures  of   mature 
organs,  like  bending  of  pulvini  of  leaves,  and  sudden  movements  like 


240      BRIEF  OUTLINE  OF   VEGETABLE  PHYSIOLOGY 

those  of  tentacles,  some  stamens,  and  leaves  of  the  Sensitive  Plant  are 
due  to  alterations  in  tissue  tensions  independent  of  growth. 

581.  Movements  may  be  due  :   (1)  to  internal  causes,  or  (2)  to  ex- 
ternal influences.     The  first  are  spontaneous,  the  second  induced. 

582.  Spontaneous  growth  movements.  —  Darwin  showed  that  the 
tips  of  growing  parts  of  plants  —  stems,  leaves,  roots  —  perpetually 
move  in  irregular  elliptical  curves.     Since  the  motion  is  one  of  bow- 
ing toward  all  points  of  the  compass  in  turn,  he  called  it  circurnnutation. 

583.  Induced  growth  movements.  —  These  are  much  the  more  strik- 
ing.    The  exciting  causes  {stimuli)  are  chiefly :  gravity,  light,  mois- 
ture, mechanical  contact,  and  variations  of  light  and  heat. 

584.  Gravity.  —  It  has  been  observed  from  actual  experiment  in 
the  laboratory  that  roots  of  seedlings  turn  toward  the  center  of  the 
earth,  while  the  plumule  turns  toward  the  zenith.     All  turnings  under 
influence  of  gravitative  force  are  manifestations  of  Geotropism.      The 
root  is  said  to  be  positively,  the  shoot  negatively,  geotropic. 

585.  Light.  —  Plants  turn,  as  we  say,  instinctively  toward  the  light. 
If  one  could  observe  the  root,  however,  it  would  be  found  to  turn  away 
from  light.     These  actions  are  instances  of  Heliotropism.     The  shoot 
is,  in  general,  positively  heliotropic,  the  root  negatively  hdiotropic. 

586.  Moisture.  —  The  root  seeking  moisture  displays  Hydrotropiwn, 

587.  Contact.  —  When  the  revolving  end  of  a  tendril  or  a  twining 
stem  strikes  an  object  of  support,  growth  on  the  touched  side  is  re- 
tarded.    The  effect  of  this  stimulus  is,  therefore,  to  make  the  tendril 
or  stem  encircle  the  support. 

588.  Variations  of  light  and  heat  modify  the  rate  of  growth  on  oppo- 
site sides  of  leaves.     If  the  upper  surface  of  blade  and  petiole  grows 
faster  than  the  lower,  the  whole  leaf  is  depressed ;  if  the  lower  side 
grows  faster,  the  leaf  is  raised.     Movements  of  this  sort  are  especially 
noticeable  in  floral  leaves.     In  warm  sunshine,  for  example,  the  leaves 
of  the  Dandelion  head  unfold  for  the  visits  of  insects;  but  when,  in 
the  afternoon,  the  light  and  warmth  fall  off  somewhat,  the  bracts  and 
corollas  of  the  inflorescence  close  up  tightly.    In  other  cases  the  effects 
of  illumination  are  just  the  reverse,  for  the  flowers  open  at  night, 
when  the  nightfliers  that  pollinate  them  are  abroad. 

589.  Movements  due  to  change  of  turgidity.  —  These  have   been 
described  in  the  chapter  on  the  leaf  (sleep  movements,  behavior  of 
the  Sensitive  Plant,  action  of  insectivorous  leaves).    Such  movements, 
due  to  changes  of  turgidity  (apart  from  growth),  are  confined  to  leaves 
(vegetative  and  floral)  ;  and  they  result  from  the  sudden  escape  of 
water  from  the  swollen  tissues  of  the  pulvinus  or  other  motile  organ, 
into  the  internal  ducts  or  intercellular  spaces. 

590.  Irritability.  —  All  the  movements  and  changes  of  movement 
referred   to  in  §§  583~589,  occasioned  by  external  exciting  causes 
(stimuli),  are  manifestations  of  the  irritability  inherent  in  protoplasm. 


APPENDIX 

I.    PHANEROGAMIC  LABORATORY  STUDIES1 

Laboratory  outfit.  —  Each  pupil  needs  a  simple  microscope.  This 
may  be  an  inexpensive  lens,  or  combination  of  lenses,  mounted  over 
a  glass  stage,  and  supplied  with  light  from  below  by  a  mirror.  Dis- 
secting microscopes  of  this  sort,  of  various  degrees  of  excellence,  are 
offered  by  dealers.  (Bausch  &  Lomb,  manufacturers,  Rochester,  N.Y. ; 
Queen  &  Co.,  manufacturers,  Philadelphia ;  Franklin  Educational  Com- 
pany, and  L.  E.  Knott  Apparatus  Company,  Boston;  Cambridge 
Botanical  Supply  Company,  Cambridge,  Mass. ;  and  others.)  Those 
forms  in  which  the  lens  is  easily  removed  from*  the  holder,  so  as  to  be 
used  as  a  hand  lens,  have  a  decided  advantage  in  examining  material 
that  is  not  readily  manipulated  on  the  stage.  Lenses  that  screw  into 
the  holder,  or  frame,  are  not  easily  got  out  for  hand  use.  The 
best  that  the  school  can  afford  in  the  way  of  a  dissecting  microscope 
is  not  too  good.  On  the  other  hand,  even  a  cheap  lens,  unmounted, 
will  help  one  to  learn  much. 

The  outfit  for  each  pupil  comprises  also  a  pair  of  dissecting  needles 
(which  may  be  homemade,  from  No.  10  cambric  needles  and  pine 
handles)  ;  a  well-sharpened  knife  or  scalpel;  and  a  pair  of  steel  forceps 
with  slender,  roughened  points.  At  hand  should  be  a  glass  of  water 
and  a  small  bottle  of  iodine  solution  (see  Exercise  II.,  2,  p.  246).  The 
laboratory  should  have  glass  slides  and  cover  glasses,  and  one  or  two 
sharp  razors,  with  means  of  keeping  the  latter  in  good  cutting  condition. 

The  experiments  call  for  various  utensils  which  need  not  be  men- 
tioned here. 

Notebooks  should  be  of  good  size  (about  8x  10  inches),  so  bound  as 
to  lie  flat  when  open  on  the  table,  and  made  of  a  good  quality  of 
paper.  J.  H.  Schaffner,  of  Ohio  State  University  (Columbus),  has 
described  (Jour.  Appl.  Micros.,  June,  1900)  what  appears  to  be  a  con- 
venient notebook.  Covers,  sheets  for  notes,  and  sheets  for  drawings 
are  separate,  of  the  same  size,  and  punched  alike.  The  whole  is  held 
together  by  shoestrings.  Dr.  Ganong  also  has  designed  a  notebook. 
It  may  be  had  of  the  Cambridge  Botanical  Supply  Company.  The 
paper  on  which  drawings  are  to  be  made  should  be  a  rag  paper,  at 

i  For  Cryptogamic  studies,  see  II.,  p.  258.  Additional  implements  are 
there  described. 


242  APPENDIX 

least  as  good  as  the  grade* known  as  ledger  17x22  —  32.  The  J.  L. 
Hammett  Company  (educational  supply),  Boston,  can  furnish  books 
of  this  paper,  8x10,  100  pages,  with  flexible  covers,  at  40  cents  each, 
more  or  less,  if  ordered  in  lots.  I  mention  this  to  give  some  notion 
of  the  probable  cost  of  such  books. 

The  Laboratory  Studies  have  been  written  with  a  view  to  the  use 
of  the  dissecting  microscope,  or  hand  lens,  solely.  But  it  is  evident 
that  one  or  two  compound  microscopes  may  be  the  means  of  adding 
greatly  to  the  interest  of  the  pupils.  Demonstrations  of  the  minute 
structure  of  the  higher  plants,  in  the  course  of  the  study  of  the  chap- 
ter on  that  subject,  demand  the  compound  instrument.  How  far  one 
may  profitably  go  into  the  study  of  cellular  structure  depends  upon 
circumstances,  such  as  the  age  of  the  pupils  and  the  time  at  their  dis- 
posal. Personally,  I  believe  that,  especially  if  the  teacher  has  used 
the  compound  microscope  much,  he  will  be  likely  to  underestimate 
the  difficulties  of  gaining  true  impressions  of  the  structure  as  it  exists 
in  three  dimensions,  from  sections  necessarily  showing  but  one  plane 
at  a  time.  . 

Material.  —  The  material  for  study,  when  not  named  and  described 
in  the  exercises  themselves,  is  specified  in  the  Appendix. 

Material  in  stock.  —  Dried  and  pressed  specimens,  supplementary  to 
the  laboratory  and  the  text,  should  be  mounted  on  stiff  board  of  con- 
venient size.  Herbarium  paper  is  too  flexible  and  too  large  for  hand- 
ing around.  The  collecting  instinct  is  strong,  arid  the  successive 
classes  in  botany  may  be  called  upon  to  build  up  such  a  collection  as 
is  desired,  in  the  case  of  schools  in  or  near  the  open  country.  Valu- 
able suggestions  as  to  collecting  and  mounting  illustrative  material 
is  given  by  Dr.  Ganong  in  the  "  Teaching  Botanist." 

Material  not  dried  may  be  preserved  in  formaline  (formaldehyde) 
of  4%.  As  sold,  this  preservative  is  of  40%.  It  is  cheaper,  when 
dilute,  than  alcohol,  but  the  fumes  are  disagreeable  and  harmful,  so 
that  material  to  be  worked  over  should  be  well  soaked  and  freed  from 
formaline.  Alcohol  is  the  best  preservative.  Fifty  per  cent  may  be 
strong  enough  to  keep  material  for  general  morphological  work ;  but 
70%  is  better. 

Study  and  drawing.  —  The  aim  of  laboratory  work  in  botany  is  to 
win  an  insight  into  the  life  of  plants  as  revealed  in  structure,  or  as 
manifested  by  living  plants  under  observation  in  the  experiments. 
Structure  is  the  record  of  past  and  present  natural  history.  It  repays 
thoughtful  consideration.  The  simple  drawing  of  the  material  pre- 
sented is  by  no  means  an  adequate  method  of  dealing  with  it.  It  ig 
common  to  see  students  draw  assiduously  and  well,  while  passing  on 
from  one  subject  to  the  next,  with  little  or  no  comprehension  of  the 
meaning  of  the  forms.  It  is  not  unusual  to  see  careful  drawings,  on 
which  much  time  has  been  put,  which  illustrate  accidental,  abnormal, 


PHANEROGAMIC  LABORATORY  STUDIES  243 

or  inconsequential  features  merely.  Such  drawing  is,  of  course,  a 
waste  of  time.  The  corrective  is  such  study  of  the  material  as  will 
insure  an  understanding  of  its  meaning  before  the  drawing  is  begun. 
When  the  essential  points  have  been  grasped,  they  are  fixed  in  the 
memory  by  drawing. 

It  is  true  that  drawing  is  a  help  in  studying  objects;  for  the  strict 
heed  one  must  pay  to  their  forms  in  order  to  represent  them  exactly 
leads  to  the  discovery  of  facts  that  would  otherwise  escape  notice. 
The  work  of  the  pencil  serves  as  a  score  by  which  we  keep  account  of 
the  degree  to  which  the  eye  has  exhausted  the  details  of  the  object. 
The  practice  of  drawing  thus  acts  as  a  means  of  increasing  the  power 
of  attention  to  the  manifold  separable  aspects  of  anything  we  wish  to 
examine,  —  that  is,  the  analytical  power.  Yet,  in  general,  in  order  that 
the  drawing  may  be  done  intelligently,  a  certain  amount  of  prelimi- 
nary study  is  necessary.  This  requires  time ;  but  the  time  so  spent 
is  likely  to  be  well  employed. 

The  attempt  has  been  made  in  this  book,  by  brief  discussions  pre- 
ceding the  exercises  and  by  suggestive  questions,  to  direct  the  pupil's 
mind  toward  the  quarter  where  the  most  essential  points  are  to  be 
looked  for  in  many  cases.  When  questions  are  asked  they  are  in- 
tended to  be  answered,  sooner  or  later,  in  the  written  notes  of  study. 

For  the  record  of  laboratory  work  should  consist  of  notes  illustrated  by 
properly  labeled  drawings.  The  notes  should  be  as  full  as  is  con- 
sistent with  time  limitations. 

In  examining  the  material,  even  when  the  desired  observations  may 
be  fairly  well  made  with  the  naked  eye,  pupils  should  be  reminded  to 
make  free  use  of  the  hand  lens,  or  the  microscope  lens  used  as  such. 
Very  many  things  are  thus  rendered  striking  and  memorable  that 
otherwise  would  fail  of  making  much  impression.  For  example,  the 
delicacy  of  the  veining  of  the  cotyledons  of  Ricinus  in  the  embryo  is 
far  better  seen  by  aid  of  the  lens  than  with  the  eye  alone,  though  the 
cotyledons  themselves  are  well  above  the  microscopic  range.  And 
this  delicate  veining  suggests  more  forcibly  than  the  mere  external 
form  of  the  embryo  how  highly  organized  and  perfected  the  young 
plant  already  is. 

Drawings  should  be  in  outline  with  little  or  no  shading  as  a  rule. 
Every  line  should  be  distinct  and  definite,  and  represent  an  exact 
observation  made  upon  the  object.  General  impressions  are  not 
sought.  Artistic  "  effects "  are  out  of  place  in  scientific  drawings. 
Every  part  should  be  labelled. 

Experiments.  —  The  best  general  manual  of  experiments  in  vege- 
table physiology  is  probably  that  of  Detmer  ("Practical  Plant  Physi- 
ology "),  translated  by  Moor,  published  by  The  Macmillan  Company, 
New  York,  1898.  List  price,  $3.00.  From  this  source  the  teacher 
will  gain  idea^s  for  additions  to  the  experiments  suggested  in  this 


244  APPENDIX 

book ;  and,  further,  will  there  find  clear  and  authoritative  statements 
of  physiological  theory.  The  book  is  more  than  a  manual  of  experi- 
mental procedure. 

Experiments  sometimes  fail  to  convince  the  pupil  of  the  truth 
which  it  is  sought  to  illustrate.  Doubts  should  not  be  put  aside  or 
left  unsatisfied  when  it  is  possible  that  some  further  test  —  which, 
oftentimes,  the  pupil  himself  is  able  to  suggest — may  settle  the  ques- 
tion without  recourse  to  the  statements  of  the  authorities.  A  little 
experimenting  along  an  original  line,  that  is,  a  line  original  as  far  as 
the  pupil  is  concerned,  is  often  of  very  great  value :  it  awakens  and 
stimulates  the  scientific  spirit  strongly  in  some  cases. 

Books  of  reference.  —  The  following  will  be  useful  to  the  teacher 
who  wishes  to  extend,  by  reading,  a  scanty  knowledge  of  botany: 
"Gray's  Structural  Botany";  American  Book  Company,  New  York. 
"Goodale's  Physiological  Botany";  American  Book  Company,  New 
York.  Strasburger  (and  others),  "  Text-book  of  Botany,"  translated 
by  Porter ;  The  Macmillan  Company,  New  York. 

This  list  might,  of  course,  be  indefinitely  extended. 

Ganong's  "  The  Teaching  Botanist "  is  a  manual  for  the  teacher, 
containing  outlines  of  a  course  of  study,  pedagogical  suggestions, 
a  list  of  books  of  reference,  etc.,  etc.;  the  book  is  highly  recom- 
mended to  teachers  in  secondary  schools.  Published  by  Macmillan, 
New  York. 

Chapter  I.  —  In  approaching  a  series  of  studies  on  a  given  topic  we 
may  adopt  either  of  two  courses.  First,  we  may,  without  delay  or 
preliminary  consideration,  proceed  to  the  actual  study  of  the  material, 
leaving  all  general  views  aside  until  the  laboratory  work  has  been 
completed  and  the  summarization  is  to  be  made.  Or,  secondly,  we 
may  seek  to  gain  at  least  some  general  idea  of  the  direction  and  aim 
of  our  investigations  before  they  are  actually  begun.  If  the  teacher 
chooses  the  former  method  he  will  pass  over  the  questions  asked  at  the 
beginning  of  Chapter  I.,  and  will  not  necessarily  emphasize  the  head- 
ings of  the  several  exercises.  If  the  second  method  is  pursued,  then 
the  teacher  will  talk  over  the  proposed  work  on  the  subject  of  seeds 
with  the  class  before  the  first  exercise.  It  will  probably  be  found  that 
amongst  them  the  pupils  already  know  a  good  deal  of  the  natural  his- 
tory of  seeds.  And  this  knowledge  may  be  made  the  basis  of  inter- 
esting suggestions  of  study.  There  may  be  a  doubt  on  the  part  of 
some  pupils  as  to  whether  the  seed  has  a  complete  plant  in  it.  This 
may  then  be  left  for  investigation.  But  all  will  doubtless  admit  that 
the  seed  contains  at  least  the  starting-point  of  a  new  plant,  if  no 
more.  Assuming  this,  the  idea  of  the  resting  state  (see  text  on 
Seeds,  Chapter  II.)  may  perhaps  be  hinted  at.  This  conception, 
together  with  the  idea  of  the  feebleness  of  the  young  plantlet  at  the 
start  as  opposed  to  the  dangers  and  difficulties  that  surround  it,  and 


PHANEROGAMIC  LABORATORY  STUDIES  245 

the  need  of  rapid  development,  may  suggest  certain  of  the  structural 
features  which  might  be  expected  in  the  seed.  Questions  at  least  may 
be  raised,  growing  out  of  the  general  conceptions  already  formed  from 
incidental  observation,  which  will  unify  and  illuminate  the  whole 
series  of  studies  on  the  seed. 

Because  I  have  found  that  this  second  method,  that  of  approaching 
laboratory  work  with  an  idea  to  work  out,  adds  to  interest  and  intel- 
ligent appreciation,  I  have  prefaced  the  chapter  with  several  questions 
which  it  is  the  aim  of  the  exercises  to  answer.  While  the  teacher 
may  make  use  of  them  by  requiring  the  pupils  to  read  them  in 
advance,  it  would  be  much  better  to  draw  from  the  class  the  princi- 
ples of  the  subject,  using  a  recitation  period  for  the  purpose,  and 
formulating  some  general  scheme  of  work  to  cover  the  subject  of 
seeds  and  their  germination.  Of  course  under  the  guidance  of  the 
teacher  the  resulting  outline  will  assume  the  general  form  in  which 
the  laboratory  studies  have  been  cast  by  the  writer,  providing  Chap- 
ter I.  is  to  be  used  for  laboratory  directions  to  the  pupil. 

I  would  suggest  that,  similarly,  at  the  beginning  of  each  of  the 
chapters  of  laboratory  studies,  time  enough  be  taken  to  gain  an  out- 
look over  the  whole  of  the  field  about  to  be  entered.  In  the  prepara- 
tory conferences  interesting  points  may  sometimes  be  introduced  by 
illustrative  material,  even  in  cases  where  closer,  more  detailed  study 
is  later  to  be  given  to  similar  material. 

Exercise  I.  —  Castor  Bean.  Material  from  seedsmen.  The  Castor 
Bean  should  not  be  eaten,  as  it  contains  poisonous  principles  which 
may  do  harm.  Let  the  seeds  be  boiled  in  water  for  five  minutes  for 
softening,  after  removing  a  little  of  the  testa  to  allow  the  water  to 
penetrate. — White  Lupine.  Lupinus  albus,  of  the  seedsmen.  Soak  1 
day  in  water.  —  Indian  Corn.  The  flat-fruited  Southern  or  Western 
variety  of  Indian  Corn,  soaked  for  a  day  or  two.  For  the  sprouted 
condition  sow  in  soil,  damp  sawdust,  wet  sphagnum,  or  between  sheets 
of  wet  blotting  paper,  after  soaking  in  water.  Allow  from  a  week  to 
10  days.  If  the  proper  stage  of  development  is  reached  before  the 
class  is  ready  for  the  study,  keep  the  material  back  by  placing  in  a 
cool  room  (above  32°  Fahr.).  In  estimating  the  time  required  to 
grow  material  for  class  use,  one  should  remember  that,  in  general, 
moderately  high  temperatures  (70°-80°)  accelerate,  while  low  temper- 
atures retard,  germination  and  growth. 

A  teacher  writes :  "  In  the  summer  I  boil  some  corn  on  the  ear.  I 
carefully  remove  the  kernels  and  preserve  them  in  about  60%  alcohol. 
They  can  be  used  at  any  time." 

In  the  directions  for  drawing,  the  numbers  in  parentheses  indicate 
magnification  in  diameters. 

Exercise  II.  —  i.  Soak  the  Four-o'clock  seeds  1  day.  The  Sun- 
flower and  the  Peanut  are  suggested  as  having  large  exalbuminous 


246  APPENDIX 

seeds.  The  exalbuminous  seed  of  the  Norway  Maple  is  interesting  on 
account  of  the  very  small  store  of  food  in  the  embryo.  The  "  grain  " 
of  Indian  Corn, the  "seeds"  of  Four-o'clock  and  Sunflower,  the  "pea- 
nut" (including  shell),  and  the  key  of  the  Maple  are  fruits.  This 
fact  need  not  be  brought  forward,  as  the  distinction  between  fruit  and 
seed  will  be  made  plain  in  the  chapter  on  fruit.  In  the  case  of  the 
Peanut  the  question  will  arise,  how  much  is  a  single  seed  ?  Refer  to 
the  like  case  of  peas  in  a  Pea  pod.  —  2.  The  iodine  used  may  be  pre- 
pared by  dissolving  the  crystals  in  alcohol,  or,  better,  in  a  strong 
aqueous  solution  of  iodide  of  potassium,  which  may  be  had  from  supply 
companies  and  probably  from  druggists.  In  testing  for  starch,  if  the 
iodine  is  too  strong,  the  characteristic  blue  tint  will  be  obscured. 
Use  the  reagent  diluted.  In  the  Castor  Bean,  Flax,  and  Cotton,  a  con- 
siderable part  of  the  food  takes  the  form  of  oil.  In  this  connection  it 
will  be  well  to  present  facts  concerning  the  uses  of  oily  seeds,  and  of 
seeds  in  general.  Or,  better,  the  subject  may  be  assigned,  as  a  whole 
or  in  parts,  to  one  or  more  pupils  for  special  reports.  In  the  Date,  the 
reserve  matter  is  in  the  form  of  "  reserve  cellulose." 

A  test  for  proteid  matters  in  seeds  may  be  made  as  follows :  Crush 
the  kernel  of  the  given  seed  on  a  glass  slide.  Add  a  few  drops  of 
concentrated  nitric  acid,  and  allow  to  act  for  a  few  minutes.  If  pro- 
teid matter  is  present  in  quantity,  a  yellow  or  orange  color  appears, 
which  becomes  more  intense  after  the  acid  has  been  washed  off  and 
strong  ammonia  water  added.  Contrast  the  color  reaction  in  the 
kernel  of  Sunflower  seed  with  that  in  pulp  of  Potato,  when  treated 
with  nitric  acid  and  ammonia ;  also  again  when  treated  with  iodine. 
The  compound  microscope  may  be  used  in  tests  with  iodine,  and  for 
detection  of  oil. 

Exercise  III.  —  Experiment  i.  This  may  well  be  a  demonstration 
largely  prepared  by  the  teacher.  The  Beans  should  be  ready  after  2 
days'  soaking.  The  department  of  physics  or  of  chemistry  will  sup- 
ply some  sort  of  simple  hydrogen  generator.  One  may  be  made  of 
flask,  cork,  and  glass  tubing,  in  the  way  described  by  elementary 
chemistries.  Fill  the  generator  flask  pretty  well  up  with  the  acid 
solution,  in  order  to  have  as  little  air  in  the  generator  as  possible. 
(For  the  physiology  of  seeds  and  germination,  see  Goodale's  "Physi- 
ological Botany,"  Ch.  XV.)  —  Experiment  2.  Several  pupils  may  work 
together  on  such  experiments  as  this.  The  gas  given  off  by  the 
sprouting  Corn  is  the  same  as  that  from  the  human  lungs,  namely 
carbonic  acid  gas.  Respiration  is  the  same  in  both  plants  and  ani- 
mals, as  regards  the  intake  (oxygen)  and  the  exhaled  product  (carbon 
dioxide) .  (See  "  Respiration  "  Goodale,  p.  367.)  —  Experiment  3.  The 
thermometer  used  should  be  graduated  in  half  degrees  or  finer ;  or,  at 
least,  the  degree  divisions  should  be  long.  Subdivisions  of  the  spaces 
may  with  care  be  estimated  down  to  tenths  by  the  eye.  Of  course,  the 


PHANEROGAMIC  LABORATORY  STUDIES          247 

rise  of  temperature  found  in  this  experiment  is  the  direct  result  of  the 
respiratory  activity  (oxidation)  detected  in  Experiment  2.  This  ex- 
periment also  is  suitable  for  a  group  of  three  or  four  students. 

Exercise  IV.  —  For  pupils  in  groups.  Of  course  this  exercise  may 
be  extended  somewhat,  at  the  option  of  the  teacher — perhaps  as 
supplementary  work  for  fast  working  and  interested  individuals.  It 
is  likely  that  several  different  temperatures  may  be  obtained  in  differ- 
ent parts  of  the  building.  And  if  steam  heat  is  used,  it  may  be 
possible  to  arrange  matters  so  that  minimum,  maximum,  and  optimum 
temperatures  of  germination  can  be  approximately  determined. 

Exercise  V.  —  For  the  facts  and  theory  of  the  response  of  growing 
parts  to  various  external  stimuli,  see  the  text-books  under  Geotropism, 
Heliotropism,  etc.;  Goodale,  pp.  392-396,  Strasburger's  "Text-book  of 
Botany  "  (Porter),  1898,  pp.  251  et  seq. 

Exercise  VI.  —  Experiment  6.  For  an  account  of  the  green  coloring 
matter  (chlorophyll)  see  Goodale,  pp.  286  et  seq.  It  would  be  inter- 
esting to  compare  the  behavior  of  Pine  seedlings  with  those  of  com- 
mon garden  plants  in  respect  to  the  development  of  chlorophyll  in 
darkness.  It  may  take  a  month  to  get  the  pine  started. 

When  the  results  of  the  experiments  on  germination  are  in,  the 
teacher  will,  of  course,  discuss  the  teachings  of  the  experiments  with 
the  class,  making  them  points  of  departure  for  the  giving  of  a  greater 
or  less  amount  of  related  information.  The  time  taken  by  the  seeds 
mentioned  to  germinate  and  come  to  the  various  desired  stages  of 
development  will  depend  on  the  temperature  of  the  room.  The  fol- 
lowing data  will  give  some  idea  of  the  time  required.  Squash,  1  inch 
deep,  came  up  in  6  days  in  a  warmish  place.  Onion,  £  in.  deep,  was 
looping  up  well  in  9  days  in  warmth.  White  Lupine,  1^  in.  deep,  came 
up  in  7  days  in  a  rather  cool  place.  The  plants  were  erect  and  had 
spread  leaves  in  14  days.  Pea,  1  in.  deep,  was  coming  up  freely  in  6 
days.  Morning  Glory  was  up  and  had  cotyledons  spread  in  5  days. 
The  seeds  may  be  sown  at  intervals  during  two  weeks  or  so  in  boxes 
of  soil  or  wet  sphagnum.  Several  pots  may  be  sown  to  show  the 
manner  in  which  the  young  plants  come  out  of  the  ground. 

Supplementary  Topics.  —  i.  This  will  require  the  compound  micro- 
scope. Spiranthes  cernua,  or  Maiden's  Tress,  is  markedly  poly- 
embryonic.  The  embryos  are  produced  without  fertilization.  (See 
Rhodora,  December,  1900.)  The  embryos  are  seen  at  a  glance,  the  seed- 
coats  being  transparent.  Spiranthes  cernua  blooms  in  September  and 
October.  Mount  seeds  first  in  alcohol.  —  2.  The  Larch  and  Spruce 
seeds  named  germinate  readily  in  10  or  12  days. 

Chapter  III.  —  Discuss  the  subject  of  winter  buds.  Some  such  line 
of  thought  as  the  following  is  suggested :  Why  do  trees  like  the 
Maple,  Elm,  etc.,  lose  their  leaves  in  winter?  (Two  reasons,  at  least. 
For  xerophytic  conditions  in  winter,  see  p.  65.)  When  does  preparation 


248  APPENDIX 

for  the  new  leaves,  to  replace  the  fallen  ones,  begin?  Of  what  advan- 
tage would  it  be  to  have  the  new  ones  ready  for  unfolding  at  the  first 
moment  of  warm  spring  weather  ?  If  leaf  rudiments  were  formed  in 
the  fall,  what  arrangements  would  be  made  for  their  protection  ?  A 
number  of  different  devices  for  shielding  the  tender  young  leaves  01 
leaf  rudiments  will  probably  come  to  mind.  Later,  in  the  laboratory, 
it  will  be  seen  whether  in  nature  these  devices  have,  in  effect,  been 
realized.  A  cursory  examination  of  twigs  bearing  buds  may  be  made 
in  class  at  the  time  of  this  discussion. 

Exercise  VII.  —  Illustration  3.  Alternatives  are  the  Hobblebush 
(Viburnum  lantanoides),  V.  Lantana,  V.  cotinifolium,  V.  furcatum,  and 
the  Butternut  (Juglatu  cinerea). 

Exercise  IX.  —  Illustration  2.  " Dutchman's  Pipevine  "  (Aristolochia 
Sipho}. 

Exercise  X.  may  be  a  written  exercise  to  be  handed  in. 

Exercise  XI.  —  The  development  of  buds  is  a  very  interesting  subject 
for  study.  The  chief  difficulty  is  to  get  buds  to  grow  well  indoors. 
Many  buds  refuse  to  develop  at  all  in  the  early  winter,  but  make  some 
growth  later  in  the  year.  If  the  subject  is  taken  up  in  the  spring, 
material  may  be  got  from  the  trees,  and  cut  branches  may  be  forced. 
A  damp  atmosphere  favors  development.  In  March  I  have  forced 
Lilac,  Rose,  and  Am.  Larch  to  unfold  enough  for  study,  in  8  days; 
Acer  platanoides  (Norway  Maple)  —  excellent  example  of  scale  de- 
velopment—  in  about  20  days;  and  Buttonwood  (Platanus  occiden- 
talis)  in  14  days.  The  latter  gives  a  good  illustration  of  the  stipular 
nature  of  some  bud  scales,  as  its  scales  grow. 

Exercise  XIII.  —  The  White  or  Silver  Maple  and  the  Rock  or  Sugar 
Maple,  both  illustrate  the  superior  development  of  the  horizontal  buds 
and  branchlets.  The  material  should  be  selected  for  the  purpose. 
Sometimes  the  vertical  shoots  will  be  decidedly  the  stronger;  such 
examples  would  be  interesting. 

Chapter  V.  Exercise  XIV. —  The  Shepherd's  Purse  is  a  common 
weed,  widely  distributed,  appearing  very  early  in  spring  in  yards  and 
by  roadsides.  Its  root  is  much  better  for  general  morphology  than 
the  fleshy  roots  of  vegetables.  Dandelion  is  fairly  good.  If  root  hairs 
do  not  show  well,  grow  a  few  seeds  of  any  kind  in  sand,  and  call 
especial  attention  to  their  manner  of  clinging  to  the  sand,  even  when 
the  plantlet  is  pulled  up. 

Exercise  XV.  —  The  Trumpet  Flower  (Tecoma  radicans)  is  best. 
English  Ivy  (Hedera  Helix)  may  be  used. 

Exercise  XVI. —  Sweet  Potato  is  suggested.  Carrot  includes  short- 
ened stem.  Dahlia  will  serve. 

Supplementary  Subjects.  —  i.  Material  may  probably  be  obtained 
from  some  greenhouse.  The  function  of  the  roots  is  commonly  mis- 
understood. Vapor  of  water  is  not  condensed  by  them,  except  as  dew. 


PHANEROGAMIC  LABORATORY  STUDIES          249 

(See  Rhodora,  March  and  April,  1900  ;  American  Gardening,  March  17 
and  24, 1900.)  — 2.  The  material  is  best  preserved  in  alcohol. — 3.  Many 
herbaceous,  geophilous  plants  show  contraction.  Examples  must  be 
sought  in  the  teacher's  own  locality.  —  4.  Grow  seedlings  in  barely 
moist  sphagnum,  in  which  saturated  pieces  of  sponge  are  buried. 
First  sprout  the  seeds  in  water.  Place  them  above  and  at  one  side  of 
the  sponge  or  sponges,  at  varying  distances  and  in  different  directions. 
This  experiment  is  suggested  by  Dr.  R.  H.  True.  —  5.  With  a  fine 
brush  and  India  ink  mark  across  the  tip  of  the  growing  primary  root 
of  a  lately  sprouted  Bean,  at  intervals  of  1  mm.,  for  a  distance  of 
1.5  cm.  Put  the  seedling  into  a  thistle  tube,  or  glass  funnel,  with  the 
root  running  down  into  the  tube.  Over  it  place  wet  cotton,  and  cover 
the  top  of  thistle  tube  or  funnel.  Rest  this  apparatus  in  the  mouth  of 
a  jar  or  other  receptacle  containing  a  little  water,  the  supporting  jar 
or  bottle  to  be  closed  after  the  tube  or  funnel  is  admitted,  so  that  the 
water  will  not  be  lost  by  evaporation.  In  24  hours,  note  the  region 
where  elongation  has  taken  place :  measure  the  spaces.  Repeat  this 
observation  after  24  hours  more.  —  6.  Place  a  young  Tropseolum 
plant  under  a  bell  jar,  and  leave  for  a  day  or  two  in  a  fairly  warm 
place.  Drops  of  sap  are  seen  on  the  margin  of  the  leaf.  These  are 
forced  up  by  "root  pressure."  (See  Goodale,  pp.  264-268,  also 
Chapter  XVIII.  of  this  book.) 

Chapter  VII.  Exercise  XVIII.  —  Balsam  (Jmpatiens)  is  better  than 
Begonia,  though  the  latter  is  commoner  in  cultivation.  Young  shoots 
of  the  Pipevine  (Aristolochia  SipTio)  may  be  got  at  the  proper  season 
and  preserved  for  use.  The  Asparagus  meant  is  the  garden  species, 
the  young  shoots  of  which  may  be  had  from  the  market  and  preserved. 
Indian  Corn  is  equally  good,  or  better.  Permanently  mounted  cross 
sections  of  both  stems  may  be  used.  If  the  pupils  cut  their  own,  the 
scalpels  must  be  very  sharp,  and  should  be  wet  when  cutting. 

Exercise  XIX.  —  This  exercise  may  be  omitted  at  the  discretion  of 
the  teacher.  If  taken,  the  block  of  wood  may  be  of  Oak,  about  1£  inch 
in  each  dimension,  cut  so  that  two  faces  are  at  right  angles  to  the 
grain,  two  are  vertical-radial,  and  two  vertical-tangential  in  the  tree. 
The  surfaces  should  be  accurately  cut  in  the  given  planes,  and 
smoothly  finished. 

Exercise  XX.  —  The  Balsam  is  the  best  stem  for  this  exercise ;  it 
may  be  had  from  greenhouses,  or  grown  in  the  schoolroom  from  seed. 
Other  growing  plants  may  be  used.  A  solution  of  red  ink  may  be 
used,  but  is  inferior  to  eosin  (from  supply  companies).  One  ounce 
eosin  will  color  three  quarts  of  water. 

Exercise  XXI. — Experiment  9.  The  more  freely  the  plant  used  is 
growing,  the  better  for  this  experiment.  "Nasturtium  "  =  Tropceolum. 
On  geotropism  see  Goodale  and  Strasburger,  as  before  cited.  — 
Experiment  10.  Other  growing  flower  scapes  may  be  found.  The 


250  APPENDIX 

Dandelion  will  answer,  if  young.  Shepherd's  Purse  I  have  found 
especially  sensitive  to  light.  Discuss  geotropism  and  heliotropisni 
with  class  after  these  experiments. 

Exercise  XXII.  —  Illustration  i.  Grass  rhizomes  will  do.  Iris  is  ex- 
cellent, as  it  shows  how  the  plant  is  propagated  by  lateral  as  well  as  ter- 
minal buds.  Useful  examples  of  rhizomes1  will  be  found  in  any  piece  of 
woods,  under  or  in  the  leaf  mold.  Subterranean  stems  (Uvularia, 
Smilacina,  Polygonatum,  Sanguiuaria,  etc.)  are  particularly  interesting. 
Keep  in  alcohol,  rather  than  dry.  For  comparison  with  rhizomes  intro- 
duce such  a  caudex  as  Plantain.  Also  subterranean  things  like  Trillium, 
Jack-in-the-pulpit  (beware  of  tasting).  —  Potato  tuber.  Artichoke 
(from  seedsmen  or  the  market)  may  be  substituted  with  advantage. 
New  potatoes  from  the  garden  have  scales ;  others  may  not  have.  — 
Houseleek.  May  be  ordered  several  months  in  advance  from  com- 
mercial growers.  As  an  alternative,  Strawberry  (pressed  or  alco- 
holic) is  suggested.  —  Asparagus.  From  florists  :  the  large  decorative 
species  known  as  Asparagus  Sprengeri  is  the  best.  —  Crocus.  From 
seedsmen,  at  about  1  cent  each.  Gladiolus  and  Montbretia  are  as 
good  but  cost  about  2  cents  each.  —  Flowering  Quince.  The  common 
Thorn,  or  the  Honey  Locust  (Gleditschia)  may  be  used.  —  Boston 
Ivy.  Or  the  Grape ;  in  which  case  the  tendrils  coil,  without  disks. 
The  Virginia  Creeper  (Ampelopsis  quinquefolia)  is  figured  in  the  text; 
otherwise  it  would  do  for  the  present  study.  In  all  these  cases  the 
tendril  is,  originally,  the  termination  of  the  main  stem,  but  is  finally 
turned  aside  by  the  growth  of  a  lateral  bud,  which  carries  on  the 
growth  of  the  vine.  The  effect  is  to  make  the  tendril  seem  to  spring 
laterally,  from  opposite  a  leaf.  The  twisting  of  tendrils  involves  an 
interesting  question.  (See  the  text.)  Why  the  double  twist,  often 
seen  ?  Hold  both  ends  of  a  string  fast  then  twist  it  by  rolling  at  its 
middle;  is  the  twist  of  entire  string  single  or  double? 

Chapter  IX.  Exercise  XXIII.  —  Experiment  1 1.  Tropceolum  is  meant. 
Several  pupils  may  work « together.  Chlorophyll  is  extracted  more 
rapidly  by  alcohol  in  a  test  tube  immersed  in  hot  water.  Then,  to 
swell  starch  grains,  boil  the  bleached  leaf  in  water.  For  carbon 
assimilation,  or  photosynthesis,  see  Goodale,  Ch.  X.,  also  the  con- 
cluding chapter  in  this  book.  For  the  liberation  of  oxygen  as  a 
measure  of  assimilation,  and  directions  for  a  most  valuable  experi- 
ment (easy  to  perform  if  material  is  available),  see  Goodale,  p.  305. 

In  connection  with  the  given  experiments  on  assimilation  in  the 
leaf,  the  observation  of  starch  may  be  made  if  compound  microscopes 
are  to  be  had.  Use  starch  from  potato,  and  perhaps  from  the  pea 
also.  Starch  being  insoluble  in  water,  the  question  arises  how  the 
food  which  takes  the  form  of  starch  can  pass  from  one  part  of  the 
plant  to  another  through  the  membranes  of  the  plant  body.  (See 
Digestion,  §  560.)  Observe  digestion  with  the  compound  microscope. 


PHANEROGAMIC  LABORATORY  STUDIES          251 

Use  potato  starch.  Apply  a  solution  of  |  teaspoonful  diastase  (drug- 
gists or  supply  companies)  in  1  teaspoonful  water  —  a  few  drops  on  a 
slide.  Observe,  after  15  minutes,  the  erosion  and  disintegration  of 
many  of  the  grains. 

Experiment  12.  Respiration  takes  place  in  all  living  members  of 
the  plant.  (See  the  final  chapter  of  the  text,  this  book.) — Experi- 
ment 13.  A  Geranium  (Pelargonium},  a  Sunflower  seedling,  or  a 
Fuchsia,  is  easily  got.  The  experiments  on  transpiration  (which  sub- 
ject see  in  Goodale,  Strasburger,  and  this  book)  are  easily  extended, 
so  as  to  test  the  effect  of  a  number  of  conditions.  (See  Ganong  for 
further  suggestions.)  Convenient  balances  are  the  "  Harvard  trip 
scales "  (apparatus  dealers).  The  sheet  rubber  is  a  grade  or  two 
heavier  than  that  used  by  dentists. 

Experiments  13,  14,  15,  and  16  are  all  on  the  same  activity  of  the 
leaf,  transpiration.  It  will  be  well  to  have  only  one  or  two  prepara- 
tions of  each  experiment,  and  have  all  the  experiments  going  on  at 
once,  prepared  simultaneously  by  different  groups  of  pupils.  The 
essential  features  of  manipulation  are  seen  at  sight,  and  the  results 
are  obvious,  so  that  the  whole  class  may  take  notes  from  apparatus 
prepared  by  two  or  three  pupils  solel}^  The  importance  of  transpira- 
tion in  drawing  water  from  the  soil,  and  with  water  the  nutrient 
soil  salts,  should  be  discussed  when  the  results  are  all  in.  Stomatal 
regulation  may  be  brought  up  in  connection  with  the  results  of  Ex- 
periments 15  and  16,  in'  which  it  is  seen  that  the  vapor  escapes  from 
the  under  surface  largely.  —  Experiment  17.  Young  potted  Tropae- 
olums,  a  month  or  two  old.  On  heliotropism,  or  turning  occasioned 
by  light,  see  Goodale,  p.  392,  or  Strasburger,  p.  251.  The  chapter  on 
physiology,  in  this  book,  may  be  referred  to.  —  Experiment  18.  Seed- 
lings of  Mimosa  pudica  may  be  grown  to  suitable  size  in  3  or  4  weeks. 
Seeds  from  seedsmen.  Oxalis  seeds  also  from  seedsmen,  or  plants 
from  growers.  On  "sleep"  movements,  see  Goodale,  p.  409,  and 
Strasburger,  p.  270.  The  irritability  of  plants  is  a  most  interesting 
subject  of  study. 

Exercise  XXIV.  —  Of  greenhouse  material,  Hibiscus  or  Abutilon  is 
very  good  for  all  points  in  this  exercise.  Geranium  (Pelargonium) 
and  German  Ivy  (Senecio  scandens)  have  stipules.  The  veining  does 
not  show  so  well.  Of  outdoor  things,  Apple  and  Quince  have  stipules. 
Selections  of  the  best  leaves  to  illustrate  types  of  venation,  compound- 
ing, etc.,  should  be  made  in  the  summer,  and  the  leaves  pressed.  But 
for  Exercise  XXIV.  fresh  material  is  needed. 

Exercises  XXVI.  and  XXVII.  —  The  assortment  of  leaves  given  the 
pupil  will  include  parallel-  and  net-veined  examples  ;  and  of  the  latter, 
some  pinnate,  some  palmate.  Several  examples  of  each  category 
should  be  provided.  Let  some  be  lobed,  divided,  etc.,  so  as  to  suggest 
the  origin  of  compounding.  Pinnately  lobed,  palmately  lobed  forms, 


252  APPENDIX 

etc.,  suggest  corresponding  compound  forms.  This  is  meant  to  be  an 
exercise  in  systematic  grouping  on  lines  of  possible  evolution  of  leaf 
forms.  Can  transitional  forms  between  pinnate  ancl  palmate  be 
found?  The  material  will  be  selected  by  the  teacher  from  the  flora 
of  the  particular  locality. 

Exercise  XXVIII.  —  Onion.  Onion  "sets"  from  the  seedsman; 
inexpensive.  —  Acacia.  This  is  interesting  in  connection  with  the 
natural  conditions  under  which  the  phyllodineous  Acacias  grow. 
Pressed  material  may  be  used,  derived,  of  course,  from  some  green- 
house. Phyllodia  with  leaflets  may  be  found  on  some  species,  even  in 
the  adult  condition  (e.g.  A.  mebanoxylon).  See  phyllodes,  Ch.  X. 

Chapter  X.  The  special  uses  of  the  leaf,  treated  in  §§  146-153, 
may  with  great  advantage  be  illustrated  by  living  material.  Seeds 
of  Cobcea  macrostemma  may  be  bought  and  the  plant  raised  in  the 
schoolroom,  if  the  temperature  is  favorable.  Drosera  binata  may 
perhaps  be  obtained  from  florists  or  from  a  botanic  garden.  D. 
rotundifolia  rests  in  winter.  A  Wardian  case  will  keep  Droseras, 
Sarracenias,  and  Dionaeas  in  good  condition  for  observation. 

Chapter  XI.  Exercises  XXIX-XXXII.  —  Scilla  siberica  is  good  for 
these  exercises.  Order  in  the  fall,  for  spring  use,  from  florists.  Cost 
small.  Tulips  can  be  had  from  Christmas  onward.  At  wholesale 
from  commercial  growers  they  cost  about  2  cents  each,  though  more  at 
times.  Hyacinths,  not  so  good,  5-10  cents  a  spike,  November  to  May. 
The  above  are  mentioned  as  available  for  city  schools.  Scilla  is  common 
everywhere  in  gardens  in  early  spring.  Bulbs,  $1  per  100.  Of  wild 
material  for  the  first  flower  studied.  Dogtooth  Violet  (Erytlironinin} 
and  Trillium  are  also  good.  The  Liliacece,  in  general,  are  excellent. 

Exercise  XXXIII.  —  The  principles  of  anthotaxy  had  best  be  taken 
up  in  the  course  of  the  general  study  of  the  flower,  for  the  sake  of 
economy  of  material,  rather  than  as  the  subject  of  a  separate  study. 
For  the  benefit  of  city  schools,  some  information  as  to  kinds,  prices, 
etc.,  of  flowers  may  be  proffered.  Azaleas,  Christmas  to  Easter,  cheap. 
Swainsonia  (leguminous,  racemose),  all  year,  50  cents  dozen  spikes. 
Candytuft  (cruciferous,  racemose),  all  year,  25  cents  dozen  spikes. 
Nasturtium,  all  year,  25  cents  dozen.  Begonia  (cymose,  unisexual), 
any  time,  cheap.  Primula,  25  cents  pot.  Bouvardia  (umbellate),  25 
cents  dozen  heads,  all  year.  Crassula  quadrifida,  compound  cymose. 
Oxalis,  good,  cymose.  Eupatoriuui,  Stevia,  and  Chrysanthemum  frute- 
scens,  composite  heads.  The  above  are  suggested  In  case  winter 
material  must  be  used.  Buy  of  wholesale  dealers,  or  growers. 

Exercise  XXXIV.  —  The  material  must  be  gathered  at  the  flowering 
season  of  the  tree  chosen  (Larch,  Spruce,  Fir,  Pine),  in  spring,  and 
preserved  in  alcohol,  unless  used  at  once.  The  fresh,  fertile  cone 
(here  for  convenience  called  a  "flower,"  but  also  spoken  of  as  an 
inflorescence)  is  very  beautiful  in  form  and  color. 


PHANEROGAMIC  LABORATORY  STUDIES          253 

Further  work  on  the  flower  will  be  directed  toward  illustration  of 
the  principles  of  floral  structure  and  biology,  given  in  the  following 
chapter  of  text.  The  extent  and  exact  character  of  this  study  are  left 
to  the  discretion  of  the  teacher  in  view  of  the  material  obtainable. 

Systematic  Botany.  —  With  regard  to  the  study  of  Systematic 
Botany,  when  this  forms  a  part  of  the  school  course,  the  following 
suggestions  may  prove  helpful. 

In  many  schools  it  has  been  the  custom  to  require  each  pupil  to 
determine  or  'analyze"  a  certain  number  of  plants,  perhaps  a  hun- 
dred or  more.  While  this  exercise  has  value,  it  may  be  doubted 
whether  the  pupil  ordinarily  receives  from  it  information  or  training 
commensurate  with  the  time  it  requires.  Through  the  recognition  in 
recent  years  of  a  greater  and  greater  number  of  species  the  accurate 
identification  of  plants  has  become  a  matter  so  technical  as  to  require 
a  degree  of  attention  and  precision  rarely  possessed  by  elementary 
pupils.  Nevertheless,  the  teacher  should  spare  no  effort  to  impart  by 
direct  instruction  or  incidental  suggestions  as  clear  ah  idea  as  possible 
of  the  general  classification  and  relationships  of  the  plants  studied  in 
the  laboratory.  Experience  shows  that  pupils  grasp  without  difficulty 
the  more  obvious  features  which  distinguish  the  larger  families.  Thus 
it  requires  but  a  few  moments  to  show  that  nearly  all  grasslike  plants 
may  be  divided  into  three  great  families,  the  true  grasses  with  round 
stems  and  split  leaf  sheaths,  the  sedges  with  triangular  stems,  and  the 
rushes  with  regular  6-parted  flowers.  Copious  illustrative  material 
(readily  obtained  even  by  city  teachers)  should  be  given  to  the  pupils 
to  exercise  their  discriminative  powers  after  or  during  any  such  instruc- 
tion as  this.  Similarly,  it  requires  but  a  few  moments  to  show  how 
most  of  the  remaining  monocotyledons  may  be  divided  into  Liliacece 
with  superior  ovary  and  six  stamens,  Amaryllidacece  with  inferior  ovary 
and  six  stamens,  Iridacece  with  inferior  ovary  and  three  stamens,  and 
Orchidacece  with  inferior  ovary  and  one  or  two  stamens.  In  like 
manner  the  leading  families  of  dicotyledons  will  be  found  to  possess 
such  characteristic  features  as  the  peculiar  inflorescence  of  the  Umbel- 
liferce,  the  dense  heads  of  the  Composites,  the  square  stems,  opposite 
leaves,  and  aromatic  qualities  of  the  Labiatce,  or  sheathing  stipules  of 
the  Polygonacece.  Indeed  a  very  few  exercises,  in  which  the  pupil  is 
encouraged  to  sort  for  himself,  along  such  simple  lines  as  these,  great 
piles  of  mixed  flowering  plants  (including  the  commonest  dooryard 
weeds),  will  enable  him  to  determine  at  sight  the  twelve  to  twenty 
more  important  families,  which  include  four  fifths  of  the  flowering 
plants  he  is  likely  to  meet  in  after  life.  A  similar  discrimination  of 
plants  in  fields  and  woods  should,  whenever  practicable,  supplement 
laboratory  exercises.  The  pupil  will,  naturally,  make  many  mistakes 
at  first,  being  inclined,  perhaps,  to  place  a  Potentilla  in  the  Ranun- 
cuiacece,  a  Datura  in  the  Convolvulacece,  or  even  a  clover  in  the  Com- 


254  APPENDIX 

positce;  but  such  errors  may  be  turned  to  good  account  by  a  tactful 
teacher,  since  they  lead  very  naturally  to  the  consideration  of  impor- 
tant floral  differences. 

When  a  general  knowledge  of  plant  families  has  been  obtained, 
the  pupil's  attention  may  well  be  directed  to  such  large  and  well- 
marked  genera  as  Lilium,  Ranunculus,  Delphinium,  Lepidium, 
Prunus,  and  the  like,  and  he  should  be  led  to  contrast  these  with 
others  of  the  same  families.  Similarly,  species  of  two  or  three  simple 
genera  should  be  considered  as  such. 

After  this  introduction  to  classification,  the  use  of  keys  and  the 
manual  will  be  readily  grasped  by  pupils  who  are  to  pursue  the  sub- 
ject further,  and  it  may  be  suggested  to  teachers  that  greater  enthu- 
siasm in  the  study  of  local  flora  can  be  stimulated  if  the  subject  is 
optional  than  if  it  is  made  obligatory.  Special  care  should  be  exer- 
cised to  direct  the  attention  of  the  pupil  to  those  plants  which,  owing 
to  their  inconspicuous  flowers,  are  likely  to  be  overlooked  or  thought 
too  difficult  for  study.  Many  small  flowers,  such  as  those  of  Mollugo, 
Acer,  Galium,  etc.,  will  be  found  relatively  simple  and  instructive,  while 
those  of  the  far  more  showy  Fringed  Polygala,  Lady's  Slipper,  Canna, 
and  the  like,  are,  from  their  irregularity,  perplexing  and  discouraging 
to  the  beginner.  The  successful  examination  of  the  flower  of  a  plan- 
tain, rush,  or  grass,  obtained  in  the  neighborhood  of  the  schoolhouse 
will  train  the  pupil's  powers  of  observation  far  more  effectively  than 
the  dissection  of  many  showy  greenhouse  flowers. 

The  teacher's  success  in  this  work  will  be  in  a  general  way  pro- 
portionate to  his  own  knowledge  of  plants,  their  names,  and  relation- 
ships. He  is,  therefore,  urged  to  acquaint  himself  so  far  as  possible 
with  the  plants  of  his  region  by  the  use  of  the  manual.  While  a 
knowledge  of  his  local  flora  will  help  him  greatly,  an  ignorance  of  the 
names  and  affinities  of  common  plants  will  expose  him  to  frequent 
mortifying  experiences  when  questioned  by  his  pupils  and  others. 

The  importance  of  a  school  herbarium,  even  if  it  be  small  and 
comprise  but  a  few  hundred  of  the  commonest  plants,  can  scarcely  be 
overestimated.  Explicit  directions  for  the  collecting,  labeling,  and 
caring  for  the  herbarium  specimens  will  be  found  in  Gray's  "  Struc- 
tural Botany,"  pp.  370-381,  or  W.  W.  Bailey's  "  Botanizing"  (Preston 
&  Rounds  Co.,  Providence).  Until  the  teacher  has  gained  some  ex- 
perience in  identifying  species,  he  will  do  well  to  send  to  some  large 
botanical  establishment  for  determination,  duplicates  of  such  plants 
as  he  is  placing  in  the  herbarium.  There  are  several  botanical  estab- 
lishments (for  example  the  Gray  Herbarium  of  Harvard  University, 
Cambridge,  Mass.)  where  well-prepared  dried  specimens  of  native 
plants  will  ordinarily  be  identified  free  of  charge,  provided  the  speci- 
mens may  be  retained.  Each  specimen  must  show,  in  the  case  of  small 
species,  the  whole  plant,  of  larger  ones,  10  or  12  inches  of  stem  bearing 


PHANEROGAMIC  LABORATORY  STUDIES          255 

leaves  and  flower*  or  fruit.  Each  must  also  be  accompanied  by  a  label 
stating* the  place  and  date  of  collection  and  the  name  of  the  collector. 
The  labels  should,  furthermore,  bear  distinctive  numbers  by  means  of 
which  the  specialist,  who  examines  the  specimens,  can  report  to  the 
teacher  their  scientific  names  in  such  a  manner  that  they  can  be  readily 
applied  to  the  duplicating  specimens  which  the  teacher  has  retained 
under  the  same  numbers. 

Chapter  XIII.  —  Fruits  make  most  interesting  material  for  compara- 
tive studies.  Preface  the  laboratory  work  by  a  classroom  discussion. 

Exercise  XXXV.  —  Wild  Indigo.  Any  leguminous  pod  is  suitable. 
Wild  Indigo  (Baptisia  tinctoria)  is  common  on  dry,  sandy  soil.  Even 
Pea  pods  and  Bean  pods  will  do.  A  teacher  offers  the  following  sug- 
gestion. "By  collecting  pods  just  as  they  are  about  to  open,  and 
preserving  in  formaline,  one  may  keep  them  indefinitely.  When  the 
class  is  ready  for  the  study  of  seed  dispersal,  the  pods  may  be  taken 
from  the  liquid,  when  they  will  open  just  as  naturally  as  in  the  fall." 
—  Violet.  Alcoholic  material,  if  fruit  is  out  of  season.  —  Checkerberry. 
The  fleshy  part  is  calyx  and  receptacle.  —  Rose  Hip.  The  cup  is  hol- 
lowed receptacle.  The  "  seeds  "  are  the  several  achenes. 

Exercise  XXXVI.  —  Outgrowth  of  the  Testa.  Put  the  Milkweed 
and  Trumpet  Creeper  seeds  in  glass  "  sample "  tubes  or  small  vials, 
and  seal  them  up  for  class  study. 

Exercise  XXXVII.  —  Illustration  i.  Staphylea.  —  Illustration  2. 
Rumex  crispus,  though  any  Rumex  will  do.  —  Illustration  3.  Bidens, 
known  as  "  Beggar's  Ticks."  The  subject  of  this  exercise  is  one  that 
may  well  be  studied  further,  either  in  the  laboratory  from  materials 
which  the  fields  supply  in  greatest  variety,  or  in  the  field  itself. 

If  the  course  in  botany  begins  in  the  fall  and  extends  throughout 
the  year,  the  fruits  studied  in  the  field,  or  at  least  collected  for  study 
by  the  pupils,  will  in  an  interesting  way  introduce  the  work  on  seeds. 


256  APPENDIX 


II.     CRYPTOGAMIC  LABORATORY  STUDIES 

The  following  additional  utensils  and  reagents  will  be  needed:  — 

Compound  microscopes.  —  Many  of  the  studies  in  Cryptogams  may 
be  profitably  carried  out  with  good  hand  lenses,  supplemented  by  the 
figures  of  the  descriptive  text.  But  compound  instruments  will,  of 
course,  be  provided  when  possible.  Even  a  single  instrument  will  be 
a  great  gain.  The  aim  should  be  to  have  one  for  each  pupil  in  the 
laboratory  division.  The  following  makes  are  recommended  as  trust- 
worthy; there  are  others:  Bausch  &  Lomb  (Rochester,  N.  Y.,  New 
York,  Chicago)  ;  Leitz  (William  Krafft,  411  West  59th  St.,  New  York)  ; 
Reichert  (Richards  &  Co.,  46  Park  Place,  New  York);  Zeiss  (of 
dealers,  e.g.  Franklin  Educational  Co.,  Boston,  and  Eimer  &  Amend, 
New  York). 

Two  eye  pieces  (2-inch  and  1-inch)  and  two  objectives  (f  and  \  inch), 
with  double  nose  piece,  should  be  had,  at  least.  For  many  details  in  the 
arrangement  of  the  laboratory  and  equipment,  the  teacher  should  see 
some  laboratory  where  these  matters  have  been  worked  out.  For  the 
theory  and  use  of  the  microscope,  see  "  The  Microscope,"  Gage,  Corn- 
stock  Pub.  Co.,  Ithaca,  N.  Y.  Practical  rules  for  pupils  are  given  by 
Peabody  (see  under  Bacteria,  p.  257). 

Razors,  flat  on  one  side,  are  needed  if  pupils  make  sections  them- 
selves ;  together  with  strops  for  sharpening  (get  a  barber  to  hone 
razors),  pith  for  holding  objects  sectioned,  and  cheap  camel's-hair 
brushes  for  removing  sections  from  razor  to  slide. 

Alcohol  (commercial,  diluted  one  half)  may  be  kept  on  the  table  in 
2-ounce  bottles  with  pipettes  fitted  into  the  corks.  Bottles  for  potash, 
glycerine,  and  iodine,  are  made  with  ground  glass  stoppers  drawn  out 
into  droppers  (1-ounce  "  dropping  bottles  "  of  dealers),  for  15-20  cents 
each.  Put  two  1-inch  pieces  of  stick  potash  into  bottle,  and  fill  up 
with  water.  Use  glycerine  one  third  strength,  and  tinge  with  eosin. 
Prepare  aqueous  iodine  as  before  directed  (with  KI). 

Plants  for  study.  —  Material  may  be  bought  of  supply  companies 
(Cambridge  Botanical  Supply  Co.,  Cambridge,  Mass.;  Geo.  M.  Gray, 
Wood's  Roll,  Mass.;  Ithaca  Botanical  Supply  Co.,  Ithaca,  N.  Y.). 
Slides  may  be  bought  of  dealers  in  microscopical  accessories.  Material 
collected  by  the  teacher  is  best  preserved  in  70  %  alcohol.  When  the 
habitats  of  plants  recommended  for  study  are  not  mentioned  in  the 
descriptive  text,  they  are  given  below,  together  with  the  times  for  col- 
lecting, the  dates  giveu  being  applicable  to  New  England. 

Books.  —  Strasburger's  text-book  will  give  the  main  facts  on 
Cryptogams.  Bennett  and  Murray's  "Handbook  of  Cryptogamic 
Botany  "  (Longmans,  Green  &  Co.,  New  York,  .$5.00)  gives  fuller  de- 
tails. On  Algae,  see  George  Murray's  "Introduction  to  the  Study  of 


CRYPTOGAM  1C  LABORATORY  STUDIES  257 

Seaweeds."  For  a  full  treatment  of  Fungi,  see  l)e  Bary's  "Compara- 
tive Morphology  and  Biology  of  the  Fungi,  Mycetozoa,  and  Bacteria" 
(Clarendon  Press,  1887).  For  names  of  many  common  fleshy  Fungi, 
refer  to  W.  H.  Gibson's  "  Our  Edible  Toadstools  and  Mushrooms  " 
(Harper  Bros.)  ;  for  Lichens,  to  Schneider's  "  Guide  to  the  Lichens  " 
(Bradlee  Whidden,  Boston) ;  for  Mosses,  to  A.  J.  Grout's  "  Mosses 
with  a  Hand  Lens  "  (Grout,  360  Lenox  Road,  Brooklyn,  N.  Y.)  ;  for 
Ferns,  Lycopodiums,  etc.,  Gray's  "  Manual." 

346.  Nostoc.  —  Alternative,  Oscillatoria,  found  on  surface  of  mud 
where  covered  with  (especially  foul)  water,  also  on  the  surface  of 
pools,  also  as  a  slippery  coating  on  rocks  in  rapidly  flowing  streams. 
Easier  to  find  than  Nostoc.     The  former  (as  well  as  Nostoc)  often  in 
greenhouses.     It  is  an  open  question  whether  the  cell  or  the  chain  is 
the  "  individual." 

347.  Pleurococcus.  —  See  descriptive  text. 

348.  Spirogyra.  —  Conjugating  material  may  be  sought  in  late  April 
and  May.    Examine  with  the  lens  floating  masses  turning  yellowish.  — 
The  cells  treated  with  glycerine  are  plasmolyzed,  when  the  protoplasmic 
contents  is  driven  away  from  the  walls.     Emphasize  the  separability 
of  wall  and  protoplasm. 

352.  Vaucheria.  —  On  pots  in  greenhouses.  It  is  said  that  material 
showing  both  kinds  of  reproduction  mentioned  in  text,  may  be 
obtained  by  throwing  mats  of  the  plant  into  jars  half  full  of  water 
about  six  weeks  before  use,  and  placing  the  jar  in  strong  light. 

355.  Ectocarpus.  —  Sporangia  may  be  found  intercalated  in  the  fila- 
ments, as  well  as  at  the  ends  of  branches.    Gametangia  =  pleurilocular 
sporangia. 

356.  Rockweed  (Fucus).  —  Abundant  on  rocks  between  tide  marks; 
in  "  fruit "  more  or  less  throughout  the  year.     At  its  best,  perhaps,  in 
summer  and  autumn.     Break  open  the  fruiting  portions  and  examine 
with  hand  lens.  —  Wet  the  razor  with  alcohol.     Make  many  sections 
before  removing  any  from  razor,  then,  on  the  slide,  select  the  thinnest 
for  study. 

359.  Polysiphonia  may  be  found  epiphytic  on  Ascophyllum.  The 
latter  is  the  dark  (almost  black)  Rockweed,  with  thick  narrow  fronds 
without  midrib,  in  which  are  elongated,  bean-shaped  bladders.  In 
buying  Polysiphonia  specify  tetraspores. 

361.  Nemalion.  —  The  fronds  are  made  up  of  essentially  independent 
filaments.  —  Batrachospermum  may  be  used  as  alternative.     It  grows 
on  stones  in  running  brooks.     The  carpogonia  and  antheridia  are 
found  early  in  the  season  (April). 

362.  Bacteria.  —  This  subject  is  of  the  highest  practical  importance, 
and,  if  possible,  should  be  treated  with  considerable  fullness.     Dwell 
on   the  relation  of  cleanliness,  in   household  and  person,  to  health. 
The  laboratory  studies  should,  if  possible,  be  extended  in  some  such 

OUT.  OF  BOX.  —  17 


258  APPENDIX 

lines  as  those  drawn  by  J.  E.  Peabody  in  "  Laboratory  Exercises  in 
Anatomy  and  Physiology"  (Holt  &  Co.,  New  York  ;  60  cents).  The 
study  of  Bacteria  given  by  Peabody  is  highly  to  be  recommended.  By 
all  means  see  also  Journal  of  Applied  Microscopy  for  February,  1891 
(Vol.  IV.,  p.  1164). 

363.  Yeast.  —  Use  fresh  yeast  cake. 

366.  Rhizopus.  —  Use  fresh,  moist  bread.  Let  each  pupil  place  a 
piece  1  inch  square  or  so  on  the  bottom  of  a  plain  tumbler,  or,  better, 
a  small  crystallizing  dish,  covering  to  keep  moist,  two  or  three  days  in 
advance  of  use.  —  For  zygospores  —  hard  to  get  in  Rhizopus  —  Sporo- 
dinia  may  be  used.  It  is  found  growing  as  yellowish,  smoky  tufts  of 
mold  on  fleshy  fungi  in  woods.  Zygospores  may  be  found  on  the 
under  side  of  the  pileus  of  the  fleshy  fungus.  Preserve  in  alcohol. 

369.  Saprolegniaceae.  —  Allow  from  four  days  to  a  week,  according 
to  temperature,  for  the  molds  to  develop.  Or,  better,  throw  in  some 
of  the  killed  seedlings  (Tomato,  or  other  small  things)  and  insects  on 
several  successive  days,  beginning  a  week  in  advance  of  use.  Zob'spo- 
rangia  are  more  abundant  on  young  material.  The  zoospores  swim 
away  at  once  in  some  species,  and  will  not  be  found  near  by  in  a 
quiescent  state. 

372.   Peziza,  on  logs  and  sticks  in  woods  in  summer. 

375.  Microsphaera  alni,  in  late  summer  and  in  September.  Press 
the  leaves.  Uncinula,  another  fungus  of  the  same  group,  is  common 
on  Willow  leaves ;  another  form  is  on  the  under  side  of  Horse-chestnut 
leaves  (August,  September).  —  The  asci  are  essentially  like  those  of 
Peziza. 

377.  Toadstool.  —  Fresh  horse  dung  in  bowls,  under  cake  covers  (to 
keep  moist),  will  give  Coprinus  in  about  two  weeks.  Make  several 
lots  to  be  sure  of  material.  Various  molds  will  come  up  before 
Coprinus.  Wash  these  down  by  sprinkling  with  water  after  a  week. 
Take  the  young  heads  of  Coprinus  before  they  open  out,  in  order  to 
section  across  gills.  Or  get  other  material  in  summer  and  keep  in 
alcohol. 

379.  Lichen.  —  Physcia  stellaris,  or  any  expanded  form  found  on  tree 
trunks.  For  comparison  of  habit  show  such  a  form  as  Cladonia 
cristatella,  common  in  pastures,  distinguished  by  bright  scarlet  apo- 
thecia.  If  time  and  microscopes  permit,  study  the  structure  of  the 
thallus  further.  What  are  the  "  green  bodies,"  and  what  is  the  nature 
of  the  other  elements  ? 

381.  Marchantia.  —  In  fruit  (spores)  in  early  summer.  Lunularia, 
known  by  its  crescent-shaped  cupiiles,  will  serve  for  the  living  habit 
and  the  gemmae  of  this  kind  of  Liverwort.  It  is  common  in  green- 
houses. 

386.  Moss.  —  Folytrichum  commune  may  be  found  in  good  condition 
(sex  organs)  in  May.  The  fertile  shoots  are  known  by  the  flowerlike 


CRYPTOGAMIC  LABORATORY  STUDIES  259 

arrangement  of  the  leaves  at  the  summit.  The  sporogonia  are  mature 
later.  Preserve  in  alcohol,  if  necessary.  Other  mosses  (e.g.  Mnium) 
will  serve.  The  protonerna  may  be  found  in  greenhouses  and  on  soil 
where  moss  is  growing. 

390.  Fern.  —  Prothallia  are  easiest  got  in  greenhouses.  They  may 
best  be  grown  (by  the  florist)  on  potsherds.  The  smaller  prothallia 
are  likely  to  have  antheridia  alone.  For  the  spores,  use  preferably 
some  Aspidium,  taken  when  the  sori  are  youngish.  If  necessary 
preserve  this  material  in  alcohol.  In  the  Maidenhair  Fern  the  sori 
are  covered  by  the  recurved  leaf  margin  —  not  an  indusium. — If 
smallish  prothallia,  which  have  not  been  wet  for  some  time,  are  placed 
in  a  drop  of  water  on  a  slide,  the  aniherozoids  are  likely  to  be  seen ; 
use  a  low  power  of  the  compound  microscope. 

396.  Selaginella,  from  greenhouses,  in  fruit  in  early  spring  (some 
species  at  other  times).  5.  rupestris  is  found  in  dry  situations  (as 
bare  hilltops)  at  the  edge  of  ledges  in  poor  soil.  It  looks  at  a 
distance  like  a  stiff,  coarse  moss. 

400.  Lycopodium  is  the  "  ground  pine  "  used  for  Christmas  decora- 
tions. In  fruit  in  late  summer. 

402.  Equisetum  arvense  is  common  on  railroad  banks,  the  fertile 
shoots  appearing  in  early  May,  the  vegetative  shoots  later. 


INDEX   AND   GLOSSARY 


Abortive.     Imperfectly  developed.     128. 

Absorption,  by  root,  232 ;  selective,  232. 

Acaulescent.   Stemless,  or  apparently  so.  56. 

Accumbent  (cotyledon).  Having  the  edges 
against  the  radicle. 

Achene.  A  small,  dry,  hard,  1-celled,  1- 
seeded,  indehiscent  fruit.  149. 

Acicular.     Slender,  needle-shaped. 

Actinomorphic,  128. 

Aculeate.    Prickly,  beset  with  prickles. 

Acuminate.    Tapering  at  the  end.     94. 

Acute.  Terminating  in  a  sharp  or  well-de- 
fined angle.  94. 

Adaptation,  types  of,  64. 

Adnate.  United,  as  the  inferior  ovary  with 
the  calyx  tube.  Adnate  anther,  one  at- 
tached for  its  whole  length  to  the  inner  or 
outer  face  of  the  filament.  135. 

Adnation,  115. 

Adventive.  Kecently  or  Imperfectly  natural- 
ized. 

^Estivation.  Arrangement  of  parts  of  peri- 
anth in  bud.  138. 

A  late.     Winged. 

Albumen,  18. 

Albuminous  seeds,  18. 

Albuminous  substances,  formation  of,!236. 

Algae,  blue-green,  170 ;  brown,  17T ;  green, 
171 ;  red,  180 ;  unicellular,  157. 

Alternate.  Not  opposite  to  each  other,  as  se- 
pals and  petals,  or  as  leaves  on  stem.  90. 

Alternation  of  generations,  207. 

Alveolate.  Honeycombed;  having  angular 
depressions  separated  by  thin  partitions. 

Ament.  A  catkin,  or  peculiar  scaly  unisexual 
spike.  141. 

Amphitropous  (ovule  or  seed).  Half  inverted 
and  straight,  with  the  hilurn  lateral.  138. 

Amplexicaul.     Clasping  the  stem. 

Anastomosing.  Connecting  by  cross  veins 
and  forming  a  network. 

Anatomy  of  phanerogams  (ch.  xvii.),  212. 

Anatropous  (ovule).  Inverted  and  straight, 
with  micropyle  next  the  hilum.  138. 

Androecium,  109. 

Androgynous  (inflorescence).  Composed  of 
both  staminate  and  pistillate  flowers. 

Angiospermous.  Having  seeds  borne  wilhin 
a  pericarp. 

Angiosperms,  107. 

Annual.    Of  only  one  year's  duration.    44. 

Anther,  108. 

Antheridial  tubes,  189. 

Antheridium,  176,  179,  203. 

Antherozoids,  176,  178,  179.  200,  206. 

Anthesis.     Time  of  expansion  of  a  flower. 


Apetalous.    Without  petals.    129. 

Apiculate.    Ending  in  a  short,  pointed  tip. 

Apothecium,  190. 

Arachnoid.  Cobwebby  ;  of  slender  entangled 
hairs. 

Archegouium,  201,  203,  206. 

Arcuate.    Moderately  curved. 

Areolate.  Marked  out  into  small  spaces; 
reticulate. 

Aril,  152.    Arilate,  having  an  aril. 

Aristate.  Having  an  awn,  or  slender,  bristle- 
like  termination.  94. 

Articulate.    Jointed  ;  having  a  node  or  joint. 

Ascent  of  sap,  233. 

Ascomycetes.  190. 

Ascus,  190,  191. 

Aspergillus,  192. 

Assimilation,  234;  carbon,  72;  (Exp.  11), 
66. 

Assurgent.    Ascending. 

Attenuate.  Slenderly  tapering;  becoming 
very  narrow. 

Auriculate.  Having  an  ear-shaped  append- 
age. 93. 

Awl-shaped.  Narrowed  upward  from  the 
base  to  a  slender  or  rigid  point. 

Awn.    A  bristle-shaped  appendage. 

Axil,  29. 

Axile  placentation,  105. 

Axillary.     Situated  in  an  axil.    29. 

Baccate.  Berrylike ;  pulpy  throughout. 
Bacteria,  160,  184 ;  practical  study,  256. 
Barbed.  Furnished  with  rigid  points  or 

bristles,  usually  reflexed  like  the  barb  of 

a  fishhook. 

Barbellate.    Finely  barbed. 
Bark,  anatomy  of,  225 ;  falling  of  old  layers, 

226. 

Basidiomycetes,  163, 194. 
Basidium,  195. 
Bast  fibers,  219. 
Batrachospermum,  180. 
Berry,  149. 

Bidentate.    Two-toothed. 
Biennial.     Of  two  years'  duration.    45. 
Bifid.    Two-cleft. 
Big  Trees,  63. 
Bilabiate.    Two-lipped. 
Bilocellate.     Having  two  secondary  cells. 
Biloculate.    Two-celled. 
Bladderwort,  89. 
Blade,  73. 

Blue-green  Alga?,  170. 
Books  of  reference,  244.  255. 
Bract.    A  more  or  less  modified  leaf  sub- 


261 


262 


INDEX  AND   GLOSSARY 


tendiug  a  flower,  or  belonging  to  an  in- 
florescence. 120,  140. 

Bracteate.     Having  bracts. 

Bracteolate.     Having  bractlets. 

Bractlets.  Secondary  bracts,  as  on  a  pedicel 
of  a  flower. 

Bread  Mold,  160,  168. 

Brown  Algae,  158. 

Bryophytes,  198. 

Buds,  accessory,  29 ;  adventitious,  33 ;  ax- 
illary, 29;  comparative  vigor,  26;  discus- 
sion introducing  study  of,  247 ;  dormant 
condition,  30  ;  general  structure,  23 ;  grow- 
ing, 27  ;  laboratory  studies,  23  ;  latent,  32 ; 
mixed,  30  ;  naked,  81  ;  nondevelopment,  25, 
32 ;  protection,  27,  28,  31 ;  time  taken  to 
unfold,  248  ;  unfolding,  25  ;  winter,  29. 

Bulb,  60. 

Bulbiferous.     Bearing  bulbs. 

Bulblets,  58. 

Caduceous.     Falling  off  early. 

Calcarate.     Produced  into,  or  having,  a  spur. 

Calcium  oxaiate,  217. 

Callus.    A  hard  protuberance,  or  callosity. 

Calyculate.  Having  brae  ts  around  calyx,  imi- 
tating an  outer  calyx. 

Calyptra,  203. 

Calyx,  100,  110. 

Cambium,  222 ;  of  cork,  225. 

Campanulate.  Bell-shaped ;  cup-shaped ; 
with  a  broad  base.  132. 

Campylotropous  (ovule  or  seed).  So  curved 
as  to  bring  apex  and  base  nearly  together. 
138. 

Canaliculate.    Longitudinally  channeled. 

Canescent.     Hoary,  with  gray  pubescence. 

Capitate.  Shaped  like  a  head ;  collected  into 
a  head  or  dense  cluster. 

Capsule.  A  dry,  dehiscent  fruit  composed  of 
more  than  one  carpel.  151. 

Carbon  assimilation,  234. 

Carbon  dioxide,  source  of,  234. 

Carinate.  Having  a  keel  or  a  projecting  longi- 
tudinal medial  line  on  the  lower  surface. 

Carpel.  A  simple  pistil,  or  one  member  of  a 
compound  pistil.  104. 

Carpogonium,  181. 

Carpospore,  182. 

Caruncle,  152. 

Carunculate.    Having  a  caruncle. 

Caryopsis.  A  grain,  as  of  grasses ;  a  seed- 
like  fruit  with  a  thin  pericarp  adnate  to  the 
contained  seed.  150. 

Catkin.    An  ament.    141. 

Caudate.  Having  a  slender  taillike  appendage. 

Caudex.  The  persistent  base  of  an  otherwise 
annual  herbaceous  stem. 

Caulescent.     Hav'ng  a  manifest  stem. 

Caulicle,  17. 

Cauline.     Belonging  to  the  stem. 

Cell,  212;  changes  in  shape.  218;  of  ovary, 
105;  of  stamens,  136;  typical,  173. 

Cell  fusion,  220. 

Cell  sap,  216. 


Cellular  structure  of  plants,  116. 

Cellulose,  218. 

Cell  wall,  217. 

Cespitose.  Growing  in  tufts  ;  forming  mats 
or  turf. 

Chaff.  A  small,  thin  scale  or  .bract,  becoming 
dry  and  membranous. 

Chaffy.     Having  or  resembling  chaff. 

Chaloza,  137,  153. 

Chlorophyll,  23,  72. 

Chlorophyll  granules,  215. 

Chloroplastids,  215. 

Chromatophore,  173. 

Cilium,  172. 

Ciliate.     Marginallv  fringed  with  hairs. 

Ciliolate.     Minutely  ciliate. 

Cinereous.     Ash  color. 

Circinate.  Coiled  from  the  top  downward,  as 
the  young  frond  of  a  fern. 

Circumscissile.  Dehiscing  by  a  regular  trans- 
verse circular  line  of  division. 

Clavaria,  195. 

Clavate.  Club-shaped  ;  gradually  thickened 
upward. 

Claw,  132. 

Cleistogamous.  Fertilized  in  the  bud,  with- 
out the  opening  of  the  flower.  119. 

Cleft.     Cut  about  to  the  middle.    95. 

Climbers,  53. 

Club  Moss,  167. 

Coalescence.  The  union  of  parts  or  organs 
of  the  same  kind.  114. 

Cochleate.     Spiral  like  a  snail  shell. 

Collenchyma,  219. 

Columella.  The  persistent  axis  of  some 
capsules,  spore  cases,  etc. 

Coma.     i.  tuft  of  hairs.     152. 

Comose.     Furnished  with  a  coma. 

Commissure.  The  surface  by  which  one 
carpel  joins  another,  as  in  the  Urnbelliferse. 

Complete  (flower),  128. 

Components  of  plant  body,  231. 

Compound.  Composed  of  two  or  more  simi- 
lar parts  united  into  one  whole.  Compound 
leaf:  one  divided  into  separate  leaflets.  82, 
96. 

Compressed.    Flattened  laterally. 

Conceptacle,  179. 

Conduction  of  sap  in  leaf,  69. 

Conduplicate.     Folded  together  lengthwise. 

Confluent.  Eunning  into  each  other; 
blended  into  one. 

Coniferous.     Cone  bearing. 

Coniferous  flower,  102. 

Conjugation,  172,  182. 

Connate.     United  congenitally. 

Connective.  The  portion  of  a  stamen  which 
connects  the  two  cells  of  the  anther.  108. 

Connivent.  Coming  into  contact ;  con- 
verging. 

Convolute.    Rolled  up  longitudinally. 

Cordate.  Heart-shaped,  with  the  point  up- 
ward. 93. 

Coriaceous.    Leathery  in  texture. 

Cork,  225. 


INDEX  AND   GLOSSARY 


263 


Conn.  The  enlarged  fleshy  base  of  a  stem, 
bulblike,  but  solid.  60. 

Corolla.  The  iiiner  perianth,  of  distinct  or 
connate  petals.  100,  110. 

Coronifortn.    Shaped  like  a  crown. 

Corrugate.     Wrinkled  or  in  folds. 

Corticium,  195. 

Corymb.  A  flat-topped  or  convex  open  flower 
cluster,  in  the  stricter  use  of  the  word, 
equivalent  to  a  contracted  raceme,  and 
progressing  in  its  flowering  from  the 
margin  inward.  140. 

Corymbose.     In  corymbs,  or  corymblike. 

Costate.  Eibbed  ;  having  one  or  more  longi- 
tudinal ribs  or  nerves. 

Cotyledons.  The  foliar  portion  or  first  leaves 
(one,  two,  or  more)  of  the  embryo  as  found 
in  the  seed.  17. 

Cotyledons,  sleep  of,  75. 

Crateriform.  Having  the  form  of  a  shallow 
bowl. 

Creepers,  57. 

Crenate.  Dentate  with  the  teeth  much 
rounded.  95. 

Crenulate.    Finely  crenate. 

Cristate.  Bearing  an  elevated  appendage  re- 
sembling a  crest. 

Cross-fertilization,  118  ;  agencies  for,  120. 

Crossing,  effect  of,  127. 

Crown.  An  inner  appendage  to  a  petal,  or  to 
the  throat  of  a  corolla.  132. 

Crustaceous.    Of  hard  and  brittle  texturei 

Cryptogams,  13;  laboratory  studies,  157; 
(ch.  xvi.),  168;  relationship  to  phanero- 
gams, 211. 

Cucullate.    Hooded  or  hood-shaped ;  cowled. 

Culm.    The    peculiar    stem  of  .sedges   and 


Cuneate.  "Wedge-shaped;  triangular,  with 
the  acute  angle  downward.  93. 

Cupules,  200. 

Cuspidate.  Tipped  with  a  cusp,  or  sharp 
and  rigid  point.  94. 

Cuticle,  227. 

Cutleria,  178. 

Cyme.  A  usually  broad  and  flattish  deter- 
minate inflorescence,  i.e.  with  its  central 
or  terminal  flowers  blooming  earliest.  142. 

Cymose.    Bearing  cymes,  or  cymelike. 

Cytoplasm.  General  mass  of  the  protoplasmic 
cell,  aside  from  the  nucleus.  214. 

Deciduous.    Not.  persistent ;  not  evergreen. 

Decompound.  More  than  once  compound 
or  divided.  98. 

Decumbent,  declining,  but  with  the  sum- 
mit ascending. 

Decurrent  (leaf).  Extending  down  the  stem 
below  the  insertion. 

Decussate.  Alternating  in  pairs  at  right 
angles.  91. 

Definite.  Of  a  constant  number,  not  exceed- 
ing twenty. 

Deflexed.  Bent  or  turned  abruptly  down- 
ward. 


Dehiscent,  Dehiscence,  151.  Opening  regu- 
larly by  valves,  slits,  etc.,  as  a  capsule  or 
anther.  151. 

Deliquescent  trunks,  33. 

Deltoid.    Shaped  like  the  Greek  letter  A. 

Dentate.  Toothed,  usually  with  the  teeth 
directed  outward.  82,  9*. 

Denticulate.     Minutely  dentate. 

Depressed.     Somewhat  flattened  from  above. 

Determinate  (inflorescence),  139,  142. 

Diadelphous  (stamens).  Combined  in  two 
sets.  135. 

Diandrous.     Having  two  stamens.    185. 

Dicarpellary.     Composed  of  two  carpels. 

Dichotomous.     Forking  regularly  by  pairs. 

Dicotyledonous.     Having  two  cotyledons. 

Dicotyledons,  17 ;  fibrovascular  bundles  of, 
222;  plan  of  flower,  110;  stem  structure, 
47 ;  stem,  anatomy  of,  223. 

Didyinous.    Twin  ;  found  in  pairs. 

Didynamous  (stamens).  In  two  pairs  of 
unequal  length.  135. 

Diffuse.    "Widely  or  loosely  spreading. 

Digestion,  235;  (Exp.),  250. 

Digitate.  Compound,  with  the  members 
borne  in  a  whorl  at  the  apex  of  the  sup- 
port. 

Dimerous  (flower).  Having  all  the  parts  in 
twos. 

Dimorphous.     Occurring  in  two  forms.  123. 

Dioecious.  Unisexual,  with  the  two  kinds 
of  flowers  on  separate  plants.  119,  129. 

Discoid.  Eesembling  a  disk.  Discoid  head, 
in  Composite,  one  without  ray  flowers. 

Disk.  A  development  of  the  receptacle  at  or 
around  the  base  of  the  pistil.  In  Com- 
posite, the  tubular  flowers  of  the  head  as 
distinct  from  the  ray. 

Dissected.  Cut  or  divided  into  numerous 
segments.  79. 

Dissemination,  145,  153 ;  agents  of,  153 ;  by 
animals,  155 ;  by  ejection,  156 ;  by  water, 
155 ;  by  wind,  153. 

Dissepiment.  A  partition  in  an  ovary  or 
fruit. 

Distichous.     In  two  vertical  ranks. 

Distinct.    Separate ;  not  united  ;  evident. 

Divaricate.     Widely  divergent. 

Divided.     Lobed  to  the  base.    96. 

Dodder,  41. 

Dormant  condition,  seeds,  19. 

Dorsal.  Upon  or  relating  to  the  back  or 
outer  surface  of  an  organ. 

Drawing,  242. 

Drupaceous.  Kesembling  or  of  the  nature 
of  a  drupe. 

Drupe.  A  fleshy  or  pulpy  fruit  with  the  in- 
ner portion  of  the  pericarp  (1-celled  and 
1-seeded,  or  sometimes  several-celled)  hard 
or  stony.  149, 

Drupelet.    A  diminutive  drupe. 

Echinate.    Beset  with  prickles. 
Ecology.    That  part  of  botany  which  treats 
of  plants  in  their  relations  to  their  sur- 


264 


INDEX  AND   GLOSSARY 


roundings.  Of  buds,  33  ;  of  flowers,  118, 
127;  of  fruits,  153. 

Ectocarpus,  158,  178. 

Effuse.     Very  loosely  spreading. 

Egg  cell,  176,"  178,  179,  181,  189,  201. 

Elater,  210. 

Elements  composing  plants,  231. 

Emarginate.  Having  a  shallow  notch  at  the 
extremity.  94. 

Embryo,  7, 16 ;  food  for,  19  ;  of  conifers,  12  ; 
origin  of,  118. 

Embryo  sac,  118,  211. 

Endocarp.  The  inner  layer  of  a  pericarp.  149. 

Endogens,  223. 

Endosperm,  18. 

Entire.    "Without  toothing  or  division. 

Enzymes,  ferments,  236. 

Ephemeral.    Lasting  only  for  one  day. 

Epidermis,  226,  227. 

Epigynous.  Growing  on  the  summit  of  the 
ovary  or  apparently  so.  130,  134. 

Epipetalous.     Upon  the  petals.    134. 

Epiphytes,  16 ;  roots  of,  39,  40. 

Equisetum,  167,  210. 

Erose.     As  if  gnawed. 

Exalbuminous.     Without  albumen.    18. 

Excurrent.  Running  out,  as  a  nerve  of  a 
leaf  projecting  beyond  the  margin.  Ex- 
current  trunks,  33. 

Exfoliating.    Cleaving  off  in  thin  layers. 

Exocarp.  The  outer  of  two  layers  of  peri- 
carp. 149. 

Exogenous.  Growing  by  annular  layers  near 
the  surface ;  belonging  to  the  Exogens. 
223. 

Experiments,  manual  of,  243. 

Exserted.  Projecting  beyond  an  envelope, 
as  stamens  from  a  corolla. 

Extrorse.     Facing  outward.    136. 

Falcate.  Scythe-shaped;  curved  and  flat, 
tapering  gradually. 

Farinaceous.    Containing  starch ;  starchlike. 

Farinose.    Covered  with  a  meallike  powder. 

Fascicle.    A  close  bundle  or  cluster.     143. 

Fastigiate  (branches).  Erect  and  near  to- 
gether. 

Fat,  in  seeds,  19. 

Fermentation  by  Yeasts,  186. 

Ferments,  236. 

Fern  (laboratory  study),  165. 

Ferns,  204. 

Ferruginous.     Eust  color. 

Fertile.  Capable  of  producing  fruit,  or  pro- 
ductive, as  a  flower  having  a  pistil,  or  an 
anther  with  pollen. 

Fertilization,  in  Vaucheria,  176 ;  of  the  ovule, 
118. 

Fibrillose.  Furnished  or  abounding  with 
fine  fibers. 

Fibrous.  Composed  of  or  resembling  fibers. 
Fibrous  tissue :  a  tissue  formed  of  elon- 
gated thick-walled  cells. 

Fibro-vascular.  Composed  of  woody  fibers 
and  ducts.  221. 


Filament.  The  part  of  a  stamen  which  sup- 
ports the  anther  ;  any  threadlike  body.  108. 

Filamentous.     Composed  of  threads. 

Filiferous.     Thread  bearing. 

Filiform.  Thread  shaped  ;  long,  slender,  and 
terete. 

Fimbriate.     Fringed. 

FimbriUate.     Having  a  minute  fringe. 

Fistular.     Hollow  and  cylindrical. 

Flaccid.     Without  rigidity  ;  lax  and  weak. 

Flexuous.  Zigzag;  bending  alternately  in 
opposite  directions. 

Floccose.  Clothed  with  locks  of  soft  hair  or 
wool. 

Floret,  126. 

Flower  (ch.  xii.),  103;  arrangement  of  or- 
gans, 101;  coniferous,  102;  ecology,  118; 
general  morphology,  103 ;  laboratory  stud- 
ies, 99;  terminology,  128;  winter  study,  252. 

Foliaceous.  Leaflike  in  texture  or  appear- 
ance. 

Follicle.  A  fruit  consisting  of  a  single  car- 
pel, dehiscing  by  the  ventral  suture.  150. 

Follicular.    Like  a  follicle. 

Food,  for  buds,  32 ;  of  young  plant,  8 ;  stored 
in  seed,  18;  translocation,  236;  supply 
(exp.  study),  13. 

Foramen,  137. 

Forests,  seeds  in  soil  of,  19. 

Formaline,  242. 

Fornicate.  Arched  over,  as  the  corona  of 
some  Borraginaceae,  closing  the  throat. 

Free.    Not  adnate  to  other  organs. 

Frond.  The  leaf  of  Ferns  and  some  other 
Cryptogams. 

Fruit,  ecology  of,  153;  laboratory  studies, 
144;  nature  of,  147;  origin,  144. 

Fruits,  aggregate,  148 ;  drupaceous,  148 ;  in 
relation  to  dissemination,  145 ;  kinds,  147 ; 
multiple,  148;  self-burying,  154;  stone, 
148. 

Fugacious.    Falling  or  fading  very  early. 

Fungi,  183 ;  Sac  Fungi,  190. 

Funicle.  The  free  stalk  of  an  ovule  or  seed. 
137. 

Funnel-form,  132. 

Fuscous.     Grayish  brown. 

Fusiform.  Spindle-shaped ;  swollen  in  th» 
middle  and  narrowing  toward  each  end. 

Galea.  A  hooded  or  helmet-shaped  portion 
of  a  perianth,  as  the  upper  sepal  of  Aconi- 
tum,  and  the  upper  lip  of  some  bilabiate 
corollas. 

Galeate.    Helmet-shaped  ;  having  a  galea. 

Gamete,  176,  179,  188,  207. 

Gametophyte,  207. 

Gamopetalous.  Having  the  petals  of  the 
corolla  more  or  less  united.  Ill,  131. 

Gamophyllous.  Composed  of  coalescent 
leaves,  sepals,  or  petals. 

Gemma,  200. 

Gemmiparous.     Producing  gemmse. 

Geniculate.    Bent  abruptly,  like  a  knee. 

Geotropism  (Exp.  5),  11,  49,  240. 


INDEX  AND   GLOSSARY 


265 


Germination,    9 ;    conditions,    19 ;    heat    of 

(Exp.  8),  10  ;  influence  of  temperature,  11 ; 

of  Horse-chestnut,  22 ;  time  required,  247. 
Gibbous.      Protuberant  or  swollen   on   one 

side. 
Glabrate.     Somewhat  glabrous,  or  becoming 

glabrous. 
Glabrous.    Smooth;  not  rough,  pubescent, 

or  hairy. 
Gland.     A  secreting  surface  or  structure ; 

any  protuberance  or  appendage  having  the 

appearance  of  such  a  structure. 
Glandular.    Bearing  glands  or  of  the  nature 

of  a  gland. 
Glaucous.      Covered    or   whitened    with    a 

bloom. 

Glochidiate.     Barbed  at  the  tip. 
Glomerate.     Compactly  clustered. 
Glomerule.  ~  A  cymose  head.    143. 
Glutnaceous.    Furnished  with  or  resembling 

glumes. 

Glume.     One  of  the  chaffy  bracts  of  the  in- 
florescence of  Grasses. 
Granular.    Composed  of  small  grains. 
Grit  cells,  220. 
Growth  and  reproduction,  174 ;  annual,  33 ; 

conditions,  239  ;  fluctuations,  239 ;  grand 

period,  239;  of  stems,  52;  phases,  238; 

of  root  (Exp.),  35. 
Guard  cells,  228. 
Guttation  (Exp.),  35,  249. 
Gymnospermous.      Bearing    naked    seeds, 

without  an  ovary. 
Gymnosperms  (Coniferce),  102;  pistils  of, 

106. 
Gynandrous.      Having   the    stamens   borne 

upon  the  pistil,  as  in  Orchidaceae.    134. 
Gynobase.    An  enlargement  or  prolongation 

of  the  receptacle  bearing  the  ovary. 
Gynoaciuin,  109. 

Habit.    The  general  appearance  of  a  plant. 

Halophytes,  65. 

Hastate.     Like  an  arrow  head,  but  with  the 

basal   lobes    pointing   outward   nearly  at 

right  angles,  93. 

Heliotropism,  240  ;  (Exp.),  49,  68. 
Herb.     A  plant  with  no  persistent  woody 

stem  above  ground. 
Herbaceous.     Having  the  characters  of  an 

herb ;  leaflike  in  color  and  texture. 
Herbaria,  253. 
Heterocyst,  170. 

Heterogamous.  Bearing  two  kinds  of  flowers. 
Hilum.    The  scar  or  point  of  attachment  of 

the  seed.    137,153. 
Hirsute.    Pubescent  w!th  rather  coarse  or 

stiff  hairs. 
Hispid.     Beset  with  rigid  or  bristly  hairs  or 

with  bristles. 

Hispidulous.     Minutely  hispid. 
Homogamous.      Bearing   but  one  kind    of 

flowers. 

Hormogonia,  171. 
Horsetail  (Equisetum),  167. 


Hyaline.    Transparent  or  translucent. 

Hybrid.    A  crossbreed  of  two  species. 

Hydnum,  195. 

Hydrophytes,  65. 

Hydrotropism  (Exp.),  85,  240,  249. 

Hymenium,  191,  195. 

Hypha,  183. 

Hypogynous.  Situated  on  the  receptacle  be- 
neath the  ovary  and  free  from  it  and  from 
the  calyx ;  having  the  petals  and  stamens 
so  situated.  130,  134. 

Imbricate.  Overlapping,  either  vertically  or 
spirally,  where  the  lower  piece  covers  the 
base  of  the  next  higher,  or  laterally,  as  in 
the  aestivation  of  a  calyx  or  corolla,  where 
at  least  one  piece  must  be  wholly  external 
and  one  internal.  139.  • 

Immersed.  Growing  wholly  under  water; 
wholly  covered  by  the  involucral  leaves,  as 
sometimes  the  capsule  in  Hepaticae. 

Imperfect  (flower),  128. 

Incised.  Cut  sharply  and  irregularly,  more 
or  less  deeply.  95. 

Included.  Not  at  all  protruded  from  the 
surrounding  envelope. 

Incomplete  (flowers),  129. 

Incubous  (leaf).  Having  the  tip  or  upper 
margin  overlapping  the  lower  margin  of 
the  leaf  above. 

Incumbent  (cotyledons).  Lying  with  the 
back  of  one  against  the  radicle. 

Indefinite  (stamens).  Inconstant  in  number 
or  very  numerous. 

Indehiscent.  Not  opening  by  valves,  etc. ; 
remaining  persistently  closed.  148. 

Indigenous.  Native  and  original  to  the 
country. 

Induplicate.  Valvate  with  margins  project- 
ing inwards.  138. 

Indurated.    Hardened. 

Indusium,  205. 

Inequilateral.    Unequal-sided. 

Inferior.  Lower  or  below;  outer  or  ante- 
rior. Inferior  ovary:  one  that  is  adnate 
to  the  calyx,  130. 

Inflated.     Hollow  and  distended. 

Inflorescence.  The  flowering  part  of  a  plant, 
and  especially  the  mode  of  its  arrange- 
ment. 101,  139. 

Innate  (anther),  135. 

Insectivorous  plants,  86. 

Inserted.    Attached  to  or  growing  out  of. 

Integuments  (teguments),  137. 

Intercrossing,  agencies,  120. 

Internode.  The  portion  of  a  stem  between 
two  nodes. 

Intramarginal.    Within  and  near  the  margin . 

Introrse.  Turned  inward  or  toward  the 
axis.  136. 

Involucel.  A  secondary  involucre,  as  that  of 
an  umbellet  in  Umbelliferae,  142. 

Involucellate.    Having  an  involucel. 

Involucral.     Belonging  to  an  involucre. 

Involucrate.    Having  an  involucre. 


266 


INDEX  AND   GLOSSARY 


Involucre.     A  circle  or  collection  of  bracts 

surroundiug  a  flower  cluster  or  head,  or  a 

single  flower. 

Involute.     Eolled  inward.    138. 
Iodine,  in  test  for  starch,  9  ;  preparation,  246. 
Irregular  (flower).      Showing  inequality  in 

the  size,  form,  or  union  of  its  similar  parts. 

129. 
Irritability,  240. 

Keel.  A  central  dorsal  ridge,  like  the  keel  of 
a  boat ;  the  two  anterior  united  petals  of  a 
papilionaceous  flower.  133. 

Kidney-shaped.  Crescentic  with  the  ends 
broad  and  rounded ;  reniform. 

Labiate.  Lipped  ;  belonging  to  the  Labiatae. 
133. 

Laboratory  outfit,  241,  255. 

Lacerate.     Irregularly  cleft  as  if  torn. 

Laciniate.  Slashed ;  cut  into  narrow  pointed 
lobes. 

Lamella.  A  thin  flat  plate  or  laterally  flat- 
tened ridge.  194. 

Lanceolate.  Shaped  like  a  lance  head,  broad- 
est above  the  base  and  narrowed  to  the 
apex.  92. 

Lateral.    Belonging  to  or  borne  on  the  side. 

Latex  tubes,  220. 

Leaf,  71 ;  activities  of  (Exps.),  66 ;  anatomy, 
266 ;  assimilation  in  (Exp.  11),  66,  72 ;  'con- 
duction in  (Exp.  20),  69 ;  form  and  quali- 
ties, 72 ;  heliotropism  (Exp.  17),  68 ;  labora- 
tory studies,  66 ;  office,  71 ;  parts,  73  ;  res- 
piration (Exp.  12),  66;  sleep  movements 
(Exp.  18),  68;  special  uses,  70;  stability 
(Exp.  21),  69;  structure,  69;  tendril,  of 
Cobsea,  84 ;  venation,  70. 

Leaflet.  A  single  division  of  a  compound 
leaf. 

Leaves,  aquatic,  79,  80 ;  arrangement,  89 ; 
bladeless,  76;  climbing,  83  ;  compound,  70, 
82,  96 ;  disposition  in  relation  to  light,  74 ; 
division,  96 ;  duration,  89 ;  equal  illumina- 
tion, 81 ;  for  storage,  83  ;  insectivorous,  86 ; 
lobing,  96;  metamorphosed,  70;  netted 
veined,  78 ;  palmately  veined,  78 ;  parallel 
veined,  77 ;  pinnately  veined,  78 ;  shapes, 
78;  shedding  of,  89;  special  conformation, 
83;  special  uses,  83;  spinelike,  83;  terms 
used  in  description,  92. 

Legume.  The  fruit  of  the  Leguminosae, 
formed  of  a  simple  pistil  and  usually  dehis- 
cent by  both  sutures.  150. 

Leguminous.  Pertaining  to  a  legume  or  to 
the  Leguminosae. 

Lepidote.     Beset  with  small  scurfy  scales. 

Liber,  225. 

Lichens,  163,  196. 

Ligulate.     Furnished  with  a  ligule.     133. 

Ligule.  A  strap-shaped  corolla,  as  in  the 
ray  flowers  of  Composita? ;  a  thin  scarious 
projection  from  the  summit  of  the  sheath 
in  Grasses. 

Limb.    The  expanded  portion  of  a  gamo- 


petalous  corolla,  above  the  throat;  the  ex- 
panded portion  of  any  petal,  or  of  a  leaf. 

131. 
Linear.     Long    and    narrow,   with    parallel 

margins. 
Lip.     Each  of  the  upper  and  lower  divisions 

of  a  bilabiate  corolla  or  calyx  ;  the  peculiar 

upper  petal  in  Orchids. 
Liverworts,  1(54, 198. 
Lobe.    Any  segment  of  an  organ,  especially 

if  rounded.     96.    • 
Loculicidal.     Dehiscent  into  the  cavity  of  a 

cell  through  the  dorsal  suture.     151. 
Loment.      A    legume    constricted,    and    at 

length  breaking,  between  the  seeds.    150. 
Longevity  of  trees,  63. 
Lunate.     Of  the  shape  of  a  half  moon  or 

crescent. 

Lycopodium,  167,  209. 
Lyrate.    Pinnatifid  with  a  large  and  rounded 

terminal  lobe,  and  the  lower  lobes  small. 

Macrosporangium,  208. 

Macrospore,  208^ 

Marcescent.    Withering,  but  persistent. 

Marchantia,  164,  198. 

Material,  illustrative,  242,  252. 

Medullary  rays,  224. 

Membranaceous,    Membranous.     Thin    and 

rather  soft  and  more  or  less  translucent. 
Meniscoid.    Concavo-convex. 
Mericarp.    One  of  the  achenelike  carpels  of 

Umbelliferae. 
Merous.     In  composition,  having  parts ;  as, 

2-merous,  having  two  parts  of  each  kind. 
Mesophytes,  65. 
Micropyle.    The    point   upon    the    seed    at 

which  was  the  orifice  of  the  ovule.    153. 
Microscopes,  compound,  242,   255;    dealers 

in,  241 ;  simple,  241. 
Microsphaera,  162,  191. 
Microsporangium,  208. 
Microspore,  208. 

Midrib.    The  central  or  main  rib  of  a  leaf. 
Mildews,  powdery,  191. 
Mistletoe,  41. 
Monadelphous  (stamens).     United  by  their 

filaments  into  a  tube  or  column.    134. 
Monandrous,  135. 
Moniliform.     Kesembling  a  string  of  beads ; 

cylindrical  with  contractions  at  intervals. 
Monocotyledonous.     Having  but  one  coty- 
ledon. 
Monocotyledons,   17 ;  fibrovascular  bundles 

of,  222;   floral  plan,  110;  stem  structure, 

47,  223. 
Monoecious.     With   stamens   and   pistils   in 

separate  flowers  on  the  same  plant.    119, 

129. 

Morphology,  14. 
Mosses,  202. 
Movements,  239  ;  due  to  change  of  turgidity, 

240  ;  induced,  240 ;  spontaneous.  240. 
Mucilaginous,     Slimy ;  containing  mucilage. 
M  ucro.     A  short  and  small,  abrupt  tip. 


INDEX  AND   GLOSSARY 


267 


Mucronate.     Tipped  with  a  mucro.    94. 
Multifid.      Cleft  into    many   lobes    or   seg- 
ments. 

Mummy  cases,  seeds  from,  19. 
Muricate.    Kough,  with  short,  hard  points. 
Muriculate.     Very  finely  muricate. 
Mycelium,  183. 

Naked.  Bare ;  without  the  usual  covering 
or  appendages.  129. 

Nectar  glands,  125. 

Nectar,  protection  of,  125. 

Nectary.  Any  place  or  organ  where  nectar 
is  secreted.  125. 

Nectariferous.     Producing  nectar. 

Nemalion,  159. 

Nerve.  A  simple  or  unbranched  vein  or 
slender  rib.  78. 

Node.  The  place  upon  a  stem  which  nor- 
mally bears  a  leaf  or  whorl  of  leaves. 

Nodose.    Knotty  or  knobby. 

Nostoc,  157,  170. 

Notebooks,  241. 

Nucellus,  137. 

Nucleus,  116,  173,  214. 

Nut.  A  hard,  indehiscent,  1-celled,  and 
1-seeded  fruit,  though  usually  resulting 
from  a  compound  ovary.  150. 

Nutlet.    A  diminutive  nut. 

Nutrient  salts  absorbed,  232. 

Obcompressed.      Compressed  dorsiventrally 

instead  of  laterally. 
Obconically.    Inversely  conical,  having  the 

attachment  at  the  apex. 
Obcordate.     Inverted  heart-shaped,  94. 
Oblanceolate.    Lanceolate,  with  the  broadest 

part  toward  the  apex,  92. 
Oblique.     Unequal-sided  or  slanting. 
Oblong.     Considerably  longer  than  broad, 

and  with  nearly  parallel  sides.    92. 
Obovate.    Inverted  ovate.    93. 
Obovoid.    Having  the  form  of  an  inverted 

egg. 

Obsolete.    Not  evident ;  rudimentary. 
Obtuse.     Blunt  or  rounded  at  the  end.    94. 
Ocrea.     A  legging-shaped  or  tubular  stipule. 
Ocreate.    Having  sheathing  stipules. 
Ochroleucous.     Yellowish  white. 
Officinal.    Of  the  shops ;  used  in  medicine  or 

the  arts. 
Offsets,  58. 
Oil  in  seeds,  9. 
Oogonium,  176,  t79,  189. 
Oospore,  176,  179,  189. 
Oosporic  reproduction,  182. 
Opaque.    Dull ;  not  smooth  and  shining. 
Operculate.     Furnished  with  a  lid. 
Operculum.     A  lid  ;  the  upper  portion  of  a 

circumscissile  capsule.    203. 
Orbicular.     Circular.     92. 
Orchids,  roots  of,  40. 
Orthotropous  (ovule  or  seed").    Erect,  with 

the  orifice  or  micropyle  at  the  apex.    137. 
Oscillatoria,  170,  256. 


Osmosis,  230. 

Oval,  92. 

Ovary.  The  part  of  the  pistil  that  contains 
the  ovules.  104. 

Ovate.  Egg-shaped ;  having  an  outline  like 
that  of  an  egg,  with  the  broader  end  down- 
ward. 92. 

Ovoid.    A  solid  with  an  oval  outline. 

Ovule,  136 ;  fertilization  of,  118. 

Ovules,  103  ;  study  of,  99. 

Ovuliferous.     Bearing  ovules. 

Oxidation,  source  of  vital  heat,  20. 

Oxygen,  in  germination  (Exp.  1),  10,  19; 
liberated,  235;  required  by  cells,  287; 
taken  up  by  embryo,  20. 

Palate.  A  rounded  projection  of  the  lower 
lip  of  a  personate  corolla,  closing  the  throat. 

Paleaceous.    Chaffy. 

Palet.  The  upper  thin  chaffy  or  hyaline  bract 
which,  with  the  glume,  incloses  the  flower 
in  Grasses. 

Palisade  cells,  227. 

Palmate  (leaf).  Eadiately  lobed  or  divided. 
78. 

Palmately.    In  a  palmate  manner. 

Panicle.  A  loose,  irregularly  compound  in- 
florescence with  pedicellate  flowers.  142, 
143. 

Panicled,  Paniculate.  Borne  in  a  panicle ; 
resembling  a  panicle.  142,  143. 

Papilionaceous  (corolla).  Having  a  stand- 
ard, wings,  and  keel,  as  in  the  peculiar 
corolla  of  many  Leguminosae.  132. 

Papillose.  Bearing  minute  nipple-shaped 
projections. 

Pappus.  The  modified  calyx  limb  in  Com- 
posite, forming  a  crown  of  very  various 
character  at  the  summit  of  the  achene.  149. 

Parasitic.  Growing  on  and  deriving  nour- 
ishment from  another  plant.  16,  41. 

Parenchyma,  spongy,  227. 

Parietal.  Borne  on  or  pertaining  to  the  wall 
or  inner  surface  of  a  capsule.  105. 

Parted.  Cleft  nearly  but  not  quite  to  the 
base.  95. 

Partial.     Of  secondary  rank. 

Pectinate.  Pinnatifid  with  narrow,  closely 
set  segments ;  comblike. 

Pedate.  Palmately  divided  or  parted,  with 
the  lateral  segments  2-cleft. 

Pedicel.    The  support  of  a  single  flower.  140. 

Pedicellate.     Borne  on  a  pedicel. 

Peduncle.  A  primary  flowerstalk,  support- 
ing either  a  cluster  or  a  solitary  flower.  140. 

Pedunculate.     Borne  upon  a  peduncle. 

Peltate.  Shield-formed  and  attached  to  the 
support  by  the  lower  surface.  80,  93. 

Penicillium,  192. 

Pentadelphous.    Of  10  stamens.    185. 

Perennial.     Lasting  year  after  year.    45. 

Perfect  (flower).  Having  both  pistil  and 
stamens.  128. 

Perfoliate  (leaf).     Having  the  stem  appar- 

.   ently  passing  through  ^t. 


268 


INDEX  AXD   GLOSSARY 


Perianth.  The  floral  envelope,  consisting  of 
the  calyx  and  corolla  (when  present),  what- 
ever their  form.  100,  110. 

Pericarp.    The  matured  ovary.    147. 

Perigynium.  The  inflated  sac  which  incloses 
the  ovary  in  Carex. 

Perigynous.  Adnate  to  the  perianth,  and 
therefore  around  the  ovary  and  not  at  its 
base.  130,  134. 

Persistent.  Long-continuous,  as  a  calyx 
upon  the  fruit,  leaves  through  winter,  etc. 

Personate  (corolla).  Bilabiate,  and  the  throat 
closed  by  a  prominent  palate.  133. 

Petal.    A  division  of  the  corolla.    110. 

Petaloid.    Colored  and  resembling  a  petal. 

Petiolate.     Having  a  petiole. 

Petiole,  the  footstalk  of  a  leaf,  73;  move- 
ments of,  75 ;  sleep  movements,  75 ;  uses, 
74. 

Petiolule,  75. 

Peziza,  162, 190. 

Phaenogamous.  Having  flowers  with  stamens 
and  pistils  and  producing  seeds.  13. 

Phloem,  222. 

Photosynthesis  (Exp.  11),  66,  72. 

Photosynthetic  assimilation,  235. 

Phyllocladiurn,  63. 

Phyllodium.  A  somewhat  dilated  petiole 
having  the  form  of  and  serving  as  a  leaf- 
blade.  76. 

Phyllotaxy,  89. 

Physiology  (ch.  xviii.),  229. 

Pileus,  194. 

Pilose.     Hairy,  especially  with  soft  hairs. 

Pinna  (pi.  Pinnae).  One  of  the  primary  di- 
visions of  a  pinnate  or  compoundly  pinnate 
frond  or  leaf. 

Pinnate  (leaf).  Compound,  with  the  leaflets 
arranged  on  each  side  of  a  common  petiole. 
78,  97. 

Pinnatifid.    Pin nately  cleft.    96. 

Pinnule.  A  secondary  pinna ;  oneofthepin- 
nately  disposed  divisions  of  a  pinna. 

Pistil,  99,  104. 

Pistillate.  Provided  with  pistils,  and,  in  its 
more  proper  sense,  without  stamens.  129. 

Pitcher  Plants,  87. 

Pitted.  Marked  with  small  depressions  or 
pits. 

Placenta,  104. 

Placentation,  types  of,  105. 

Plasmolysis  (§  350),  158,  256. 

Pleurococcus,  157,  171. 

Plicate.  Folded  into  plaits,  usually  length- 
wise. 

Plumose.  Having  fine  hairs  on  each  side, 
like  the  plume  of  a  feather,  as  the  pappus- 
bristles  of  Thistles. 

Plumule.  The  bud  or  growing  point  of  the 
embryo.  18. 

Pod     Any  dry  and  dehiscent  fruit. 

Pollen,  100;  grain,  116,  212;  growth  of,  117; 
of  Pines,  120  ;  tube,  117. 

Pollination  by  insects,  121 ;  by  water,  120 ; 
by  wind,  120. 


Polliniferous.     Bearing  pollen. 

Pollinium  (pi.  Pollinia).     A  mass    jf  waxy 
pollen  or  of  coherent  pollen  grains,  as  in  \ 
Asclepias  and  Orchids.    136. 

Polliuoid,  1S1. 

Polyadelphous.    Having  many  stamens.   135. 

Polycotyledonous  embryo,  17. 

Polygamous.  Having  flowers,  some  of  them 
perfect,  some  staminate  or  pistillate  only. 
129. 

Polypetalous.  Having  separate  petals.  111. 
131. 

Polyporus,  196. 

Polysiphonia,  159. 

Pome.  A  kind  of  fleshy  fruit,  of  which  the 
apple  is  the  type.  149. 

Porose.     Pierced  with  small  holes  or  pores. 

Posterior.  In  an  axillary  flower,  on  the  side 
nearest  to  the  axis  of  inflorescence. 

Praemorse.     Appearing  as  if  bitten  off. 

Preserving  material,  242,  255. 

Prickle.  A  small  spine  or  more  or  less  slen- 
der sharp  outgrowth  from  the  bark  or  rind. 

Procumbent.     Lying  on  the  ground. 

Proliferous.     Producing  offshoots. 

Propagation,  by  gemmae,  200 ;  vegetative  (by 
stems),  58. 

Prostrate.    Lying  flat  upon  the  ground. 

Proteid  matter,  in  seeds,  19  ;  test  for,  246. 

Protein  granules,  216. 

Proterandry,  119. 

Proterogynous.  Having  the  stigma  ripe  for 
the  pollen  before  the  maturity  of  the  an- 
thers of  the  same  flower.  119. 

Prothalliuin,  205,  208,  209. 

Protonema,  204. 

Protoplasm,  116,  173,  213,  214. 

Pseudaxillary.  Terminal,  but  becoming  ap- 
parently axillary  by  the  growth  of  a  lateral 
branch. 

Pseudo-costate.  False  ribbed,  as  when  a 
marginal  vein  or  rib  is  formed  by  the  con- 
fluence of  the  true  veins. 

Pteridophytes,  204. 

Puberulent.    Minutely  pubescent. 

Pubescent.  Covered  with  hairs,  especially  if 
short,  soft,  and  downy. 

Pulvinus,  75 ;  action  of,  240. 

Punctate.  Dotted  with  depressions  or  with 
translucent  internal  glands  or  colored  dots. 

Puncticulate.    Minutely  punctate. 

Pungent.  Terminating  in  a  rigid  sharp 
point ;  acrid. 

Putamen.  The  shell  of  a  nut ;  the  bony  part 
of  a  stone  fruit. 

Quadrate.     Nearly  square  in  form. 

Eaceme.  A  simple  inflorescence  of  pediceled 
flowers  upon  a  common,  more  or  less  elon- 
gated axis. 

Eacemose.  In  racemes,  or  resembling  a 
raceme. 

Eadiate.  Spreading  from  or  arranged  around 
a  common  center ;  bearing  ray  flowers. 


INDEX  AND   GLOSSARY 


269 


Kadical.  Belonging  to  or  proceeding  from 
the  root  or  base  of  the  stem  near  the 
ground. 

Eadicle.  The  initial  root  of  the  embryo. 
Less  properly,  the  stem  of  the  embryo ; 
below  the  cotyledons  (caulicle).  20. 

Kameal.     Belonging  to  a  branch. 

Ramification.    Branching. 

Raphe,  153. 

Eay.  The  branch  of  an  umbel ;  the  marginal 
flowers  of  an  inflorescence  when  distinct 
from  the  disk. 

Receptacle.  The  more  or  less  expanded  or 
produced  portion  of  an  axis  which  bears 
the  organs  of  a  flower  (the  torus),  or  the 
collected  flowers  of  a  head.  112. 

Recurved.    Curved  downward  or  backward. 

Red  Algae,  159. 

Reduplicate,  188. 

Reflexed.  Abruptly  bent  or  turned  down- 
ward. 

Regular.  Uniform  in  shape  or  structure. 
128. 

Reniform.    Kidney-shaped.    93. 

Repand.  With  a  slightly  uneven  and  some- 
what sinuate  margin.  95. 

Reproduction,  174 ;  asexual,  183 ;  carpospo- 
ric,  1S2 ;  oosporic,  182 ;  sexual,  183 ;  zygo- 
sporic,  182. 

Resiniferous.    Producing  resin. 

Respiration  (Exp.  2),  10,  236 ;  in  leaves,  (Exp. 
12),  66 ;  in  germination,  20. 

Resting  periods,  238 ;  in  buds,  80  ;  seeds,  19. 

Reticulate.  In  the  form  of  network;  net- 
veined.  77. 

Retrorse.    Directed  back  or  downward. 

Retuse.  With  a  shallow  notch  at  a  rounded 
apex.  94. 

Revolute.  Rolled  backward  from  the  mar- 
gins or  apex. 

Rhachis.  The  axis  of  a  spike  or  of  a  com- 
pound leaf.  70. 

Rhizome.  Any  prostrate  or  subterranean 
stem,  usually  rooting  at  the  nodes  and  be- 
coming erect  at  the  apex.  50,  59. 

Rhizopus,  160,  186. 

Rhombic,  Rhomboidal.  Somewhat  lozenge- 
shaped  ;  obliquely  four-sided. 

Rib.  A  primary  or  prominent  vein  of  a  leaf. 
77. 

Ringent.  Gaping,  as  the  mouth  of  an  open 
bilabiate  corolla.  133. 

Rockweed,  158,  178. 

Root,  anatomy,  229  ;  conduction  (Exp.  7),  85 ; 
geotropism,  11 ;  gross  anatomy,  84;  grow- 
ing point,  89  ;  laboratory  studies,  84  ;  pri- 
mary, 36 ;  origin,  36. 

Root  cap,  39. 

Root  hairs,  22  ;  action  of,  88. 

Root  pressure,  233 ;  (Exp.),  35 ;  (Exp.),  249. 

Roots,  absorption,  37 ;  adventitious,  87 ; 
aerial,  39  ;  as  holdfasts,  42 ;  climbing,  85, 
42  ;  duration  of,  44  :  for  storage,  43  ;  func- 
tions, 37  ;  growth  (Exp.),  249  ;  origin  of 
new,  229  ;  parasitic,  40 ;  storage,  85. 


Rootstock.     Same  as  Rhizome.    59. 

Rostrate.    Having  a  beak  or  spur. 

Rosulate.     In  the  form  of  a  rosette. 

Rotate  (corolla).  W heel- shaped ;  flat  and 
circular  in  outline.  181. 

Rotund.     Rounded  in  outline. 

Rudiment.  A  very  partially  developed  or- 
gan ;  a  vestige. 

Rudimentary.     But  slightly  developed. 

Rufous.     Reddish  brown. 

Rugose.     Wrinkled. 

Runcinate.  Sharply  incised,  with  the  seg- 
ments directed  backward. 

Runner.  A  filiform  or  very  slender  stolon. 
58. 

Rusts,  192. 

Saccate.    Sac-shaped. 

Sac,  embryo,  118  ;  pollen,  108  ;  fungi,  190. 

Sagittate.     Shaped  like   an   arrowhead,   the 

basal  lobes  directed  downward.    93. 
Salver-shaped   (corolla).     Having  a  slender 

tube  abruptly  expanded  into  a  flat  limb. 

131. 

Samara.    An  indebiscent,  winged  fruit.    150. 
Sap,  ascent  of  (Exp.  8),  49,  288. 
Saprolegniaceae,  188. 
Saprophytes,  39. 
Scabrous.    Rough  to  the  touch. 
Scape.    A  peduncle  rising  from  the  ground, 

naked  or  without  proper  foliage. 
Scapose.     Bearing  or  resembling  a  scape. 
Scarious.     Thin,  dry,  and  membranaceous, 

not  green. 
Sclerotic  cells,  220. 
Scorpioid  (inflorescence).     Circinately  coiled 

while  in  the  bud.    143. 
Seed,  152;    appendages,  155;  ecology,  158; 

origin,  15 ;  processes  leading  to  formation 

of,  116 ;  study  of,  7,  145. 
Seed  coats,  how  removed  by  seedling,  22. 
Seedlings,  development,  12,  20. 
Seed  plants,  14. 
Seed  rudiments  (ovules),  15. 
Seeds,    dispersal,   158;    ejected,   155;    from 

mummy  cases,  19  ;  in  forest  soil,  19  ;  rest- 
ing state,  19 ;  store  of  food,  19 ;  vitality, 

19. 
Segment.     One  of  the  parts  of  a  leaf  or  other 

like  organ  thaj  is  cleft  or  divided,  96. 
Selaginella,  166,  207. 
Self-fertilization.  118 ;  prevented,  119. 
Sensitive  Plant  (Exp.  19),  68. 
Sepal.    A  division  of  a  calyx.    110. 
Septicidal  (capsule).     Dehiscing  through  the 

partitions  and  between  the  cells.    151. 
Septifragal.    The  valves  breaking  from  the 

septa  in  dehiscence.    151. 
Septum.    Any  kind  of  partition. 
Sequoias,  63. 

Serrate.    Having  teeth  pointing  forward.    94. 
Serrulate.     Finely  serrate. 
Sessile.    Without  footstalk  of  any  kind. 
Setaceous.     Bristlelike. 
Setose.    Beset  with  bristles. 


270 


INDEX  AND   GLOSSARY 


Setulose.     Having  minute  bristles. 

Sexual  reproduction.    183. 

Sheath.  A  tubular  envelope,  as  the  lower 
part  of  the  leaf  in  Grasses. 

Sheathing.     Inclosing  as  by  a  sheath. 

Shoot,  14 ;  metamorphosed  (§§  87-99),  58. 

Shrub.  A  woody  perennial,  smaller  than  a 
tree. 

Sieve  tubes,  238. 

Silicle.     A  short  silique. 

Silique.    The  peculiar  pod  of  Cruciferae. 

Silky.  Covered  with  close-pressed,  soft,  and 
straight  pubescence. 

Simple.    Of  one  piece  ;  not  compound. 

Sinuate.  With  the  outline  of  the  margin 
strongly  wavy.  95. 

Sinus.  The  cleft  or  recess  between  two 
lobes.  80. 

"Sleep  of  Plants,"  76. 

Sleep  movements,  75;  of  leaf  (Exp.  18),  68. 

Smooth.    Without  roughness  or  pubescence. 

Sorus  (pi.  Sori).  A  heap  or  cluster,  applied 
to  the  fruit  dots  of  Ferns.  205. 

Spadix.  A  spike  with  a  fleshy  axis.  126, 
141. 

Spathe.  A  large  bract  or  pair  of  bracts  in- 
closing an  inflorescence.  126. 

Spatulate.  Gradually  narrowed  downward 
from  a  rounded  summit.  93. 

Spermatophytes,  14. 

Spicate.    Arranged  in  or  resembling  a  spike. 

Spiciform.    Spikelike. 

Spike.  A  form  of  simple  inflorescence  with 
the  flowers  sessile  or  nearly  so  upon  a  more 
or  less  elongated  common  axis.  141. 

Spikelet.    A  small  or  secondary  spike. 

Spine.  A  sharp  woody  or  rigid  outgrowth 
from  the  stem. 

Spinose.    Spinelike,  or  having  spines. 

Spirogyra,  157,  173. 

Spongy  parenchyma,  227. 

Sporangium.    A  spore  case.    205. 

Spores,  181,  182,  187,  191,  201,  205. 

Sporidia,  194. 

Sporocarp.  The  fruit  cases  of  certain  Cryp- 
togams containing  sporangia  or  spores. 

Sporogonium,  201. 

Sporophylls,  212. 

Sporophyte,  207. 

Spur.  A  hollow  saclike  or  tubular  extension 
of  some  part  of  a  blossom,  usually  nectar- 
iferous. 

Squamula.  A  reduced  scale,  as  the  hypogy- 
nons  scales  in  Grasses. 

Squarrose.  Having  spreading  and  project- 
ing  processes,  such  as  the  tips  of  involucral 


Squarrulose.     Diminutively  sqnarrose. 

Stability  of  plant  body,  230. 

Stamen.  One  of  the  pollen-bearing  or  fer- 
tilizing organs  of  the  flower.  108. 

Stamens,  study  of,  100. 

Staminate  (flower).  Possessing  stamens  and 
no  pistil.  129. 

Staminodium.     A   sterile    stamen,,   or   any 


structure  without  anther  corresponding  to 
a  stamen. 

Standard.  The  upper  dilated  petal  of  a  pa- 
pilionaceous corolla. 

Starch,  216;  formation  (Exp.  11),  66;  in 
seeds,  19  ;  observation,  in  laboratory,  250 ; 
test,  9. 

Stellate,  Stelliforrn .    Star-shaped. 

Stem,  51 ;  anatomy,  223  ;  ascent  of  sap  (Exp. 
8),  49 ;  characteristic  features,  46 ;  endog- 
enous, 223  ;  exogenous,  223  ;  geotropism 
(Exp.  9),  49;  growth  in,  48;  heliotropism, 
49  (note) ;  internal  structure,  46 ;  labora- 
tory studies,  45. 

"Stemless"  plants,  56. 

Stems,  as  foliage,  61 ;  creeping,  57  ;  for  prop- 
agation, 58 ;  growth  of,  52 ;  twining, 
53. 

Sterile.  Unproductive,  as  a  flower  without 
pistil,  or  stamen  without  an  anther. 

Stigma,  104,  107. 

Stigmatic.  Belonging  to  or  characteristic  of 
the  stigma. 

Stimulus,  240. 

Stipe.  The  stalklike  support  of  a  pistil; 
the  leaf  stalk  of  a  Fern  ;  the  stalk  of  a  Toad- 
stool. 194. 

Stipitate.    Having  a  stipe. 

Stipular.    Belonging  to  stipules. 

Stipulate.     Having  stipules. 

Stipules,  73 ;  as  thorns,  73 ;  of  Acacias,  73 ; 
of  the  Pea,  69. 

Stolon.  A  runner,  or  any  basal  branch  that 
is  disposed  to  root.  58. 

Stoloniferous.     Producing  stolons. 

Stomates,  199,  228 ;  action,  233. 

Storage,  236  ;  in  leaves,  70. 

Striate.  Marked  with  fine  longitudinal  lines 
or  ridges. 

Strict.    Yery  straight  and  upright. 

Strigose.  Beset  with  appressed  sharp  straight 
and  stiff  hairs. 

Strobile.  An  inflorescence  marked  by  im- 
bricated bracts  or  scales,  as  in  the  Hop  and 
the  Pine  cone. 

Strophiole.  An  appendage  at  the  hilum  of 
certain  seeds. 

Style,  104. 

Stylopodium.  A  disklike  expansion  at  the 
base  of  a  style,  as  in  Umbelliferae. 

Sub-.  A  Latin  prefix,  usually  signifying 
somewhat  or  slightly. 

Subulate.    Awl-shaped. 

Succulent.    Juicy,  fleshy. 

Suffrutescent.  Slightly  or  obscurely  shrubby. 

Suffruticose.  Very  low  and  woody ;  diminu- 
tively shrubby. 

Sugar,  in  seeds,  19. 

Sulcate.    Grooved  or  furrowed. 

Sundew,  86. 

Superior  (ovary).     Free  from  the  calyx,  130. 

Suspended  (ovule).  Hanging  from  the  apex 
of  the  cell. 

Suture.    A  line  of  dehiscence. 

Syconium,  151. 


INDEX  AXL>   GLOSSARY 


271 


Symbiosis,  197. 

Symmetry,   deviations  from,   through  light 

adjustment  (§  113),  74. 
Sympodium,  143. 
Syngenesions,  135. 

Synonym.    A  superseded  or  unused  name. 
Systematic  botany,  253. 

Teguments,  137. 

Teleutospore,  194. 

Temperature,  influence  on  germination,  11. 

Tendrils,  54;  sensitiveness,  55. 

Tension  of  tissues,  230. 

Terete.    Cylindrical. 

Terminal.    At  or  belonging  to  the  apex. 

Ternate.     In  threes.    98. 

Testa,  152  ;  outgrowths  of,  145. 

Tetradynamous.     Having  four  long  and  two 

shorter  stamens.   135. 
Tetraspore,  181. 
Tetragonal.     Four-angled. 
Text-books,  244,  255. 
Thallophytes,  169. 
Thallus.    In  Cryptogams,  a  cellular  expansion 

taking  the  place  of  stem  and  foliage.     169. 
Throat.    The  orifice  of  a  gamopetalous  co- 
rolla. 
Thyrse.    A  contracted  or  ovate,  and  usually 

compact,  panicle.     143. 
Thyrsoid.    Resembling  a  thyrse. 
Tissues,  221. 
Tissue  tension,  230. 
Topics,  supplementary,  12,  33,  35. 
Tomentose.    Densely  pubescent,  with  matted 

wool. 
Torose.      Cylindrical,  with  contractions  at 

intervals. 

Torulose.    Diminutive  of  Torose. 
Torus.     The  receptacle  of  a  flower. 
Transfer  of  plant  food,  236. 
Transfer  of  water  in  plant,  232. 
Translocation  of  organic  substances  (trans- 
fer), 233,  236. 

Transpiration  (Exps.  13,  14,  15,  16),  66,  67. 
Trees,  Big,  of  California,  63  ;  longevity  of,  63. 
Triandrous.    Having  three  stamens.    135. 
Trichogyne,  181. 
Trichomes,  28,  229. 

Trifoliolate.     Having  three  leaflets.    98. 
Trigonous.    Three-angled. 
Trimorphous.     Occurring  under  three  forms. 
Triquetrous.     Having  three  salient  angles, 

the  sides  concave  or  channeled. 
Truncate.     Ending  abruptly,   as  if  cut  off 

transversely.     94. 
Tuber.    A  thickened  and  short  subterranean 

branch,  having  numerous  buds  or  eyes.   50, 

59. 

Tubercle.    A  small  tuber  or  tuberlike  body. 
Tuberiferous.     Bearing  tubers. 
Tuberous.     Having  the  character  of  a  tuber ; 

tuberlike  in  appearance. 
Tumid.    Swollen. 
Tunicated.     Having  concentric  coats,  as  an 

onion. 


Turbinate.  Top-shaped  ;  inversely  conical. 
Turgidity  (§  108),  73,  230  ;  changes  of,  240. 
Twiners,  53. 

Ulothrix,  172. 

Umbel.     An  inflorescence  in  which  a  cluster 

of  peduncles  or  pedicels  spring  from  the 

same  point.     140. 
Umbellate.    In  or  like  an  umbel. 
Umbonate.     Bearing  a  stout  projection   in 

the  center ;  bossed. 
Undulate.     With  a  wavy  surface;    repand. 

95. 
Unguiculate.    Contracted    at    base    into    a 

claw. 

Unifoliolate,  98. 
Unisexual.     Of  one  sex,  either  staminate  or 

pistillate  only.     128. 
Urceolate.     Hollow  and  cylindrical  or  ovoid, 

and  contracted  at  or  below  the  mouth,  like 

an  urn. 

Uredospore,  198. 
Utricle.    A  small,  bladdery,  1-seeded  fruit; 

any  small,  bladderlike  body. 

Vacuoles,  215. 

Valvate.  Opening  by  valves,  as  a  capsule ; 
in  aestivation,  meeting  by  the  edges  without 
overlapping.  138. 

Valve.  One  of  the  pieces  into  which  a  cap- 
sule splits.  151. 

Vascular.  Furnished  with  vessels  or 
ducts. 

Vaucheria,  158,  175. 

Vegetative  propagation,  58,  200. 

Veinlets,  77. 

Veins.  Threads  of  fibro-vascular  tissue  in  a 
leaf  or  other  organ,  especially  those  which 
branch  (as  distinguished  from  nerves). 
77. 

Venation,  70 ;  of  leaf,  76. 

Ventral.  Belonging  to  the  anterior  or  inner 
face  of  an  organ  ;  the  opposite  of  dorsal. 

Ventral  suture,  114. 

Venus' s  Flytrap,  88. 

Vernation.  The  arrangement  of  leaves  in  the 
bud. 

Verrucose.  Covered  with  wartlike  eleva- 
tions. 

Versatile  (anther).  Attached  near  the  mid- 
dle, and  turning  freely  on  its  support.  135. 

Verticfflate.     Disposed  in  a  whorl.     90. 

Vesicle.    A  small  bladder  or  an  air  cavity. 

Vesicular,  Vesiculoser  Composed  of  or 
covered  with  vesicles.  ^ 

Villous.     Bearing  long  and  soft  hairs. 

Virgate.  Wand-shaped;  slender,  straight, 
and  erect. 

Vitality  of  seeds,  19. 

Water,  in  germination,  20. 

Water  Mold,  161,  188. 

Whorl.    An  arrangement  of  leaves,  etc.,  in 

a  circle  round  the  stem,  90. 
Wing.    Any  membranous  or  thin  expansion 


272 


INDEX  AND   GLOSSARY 


bordering  or  surrounding-  an  organ ;  the 

lateral  petal  of  a  papilionaceous  corolla. 
"Wood,  annual  layers,  224 ;  structure  of,  48, 

219. 
Woolly.      Clothed    with    long   tortuous    or 

matted  hairs. 

Xerophytes,  65. 
Xylene,  222. 


Yeast,  160. 
Yeasts,  186. 

Zoosporangia,  178. 
Zoosporangium,  189. 
Zoospores,  172,  175,  179,  189. 
Zygoinorphic,  129. 

Zygospores,   172,   174,  183;    of    Sporodinia, 
357. 


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